Day Trips from Dresden?

As an alternative to Schloss Sonnenstein or Colditz might I suggest that you visit the Fortress Königstein. Königstein is an unbelievable fortification on the top of a flat mountain top east of Dresden. I understand it was sieged but never attacked. Having been there and seen the fortification, it doesn't surprise me.

@ crooney55...A very interesting itinerary you have planned. I've been to a couple of the places you mention. Dresden, Meissen, Pilnitz. Getting to Colditz can be done from Dresden Hbf. Take the train to Leipzig Hbf. Outside is a bus depot, (on the left hand side as you step out), which has one of the buses going to Colditz. I've checked out this route myself at Leipzig Hbf.

"...to Dresden for a week." Fantastic! Across the Elbe you can see in Dresden-Neustadt the biggest military history museum in Germany, which features also Saxon military history since Dresden was always a military and a strategic site. Dresden-Neustadt had hardly any damage on the night that Dresden's Zentrum was obliterated in the fire bombing. Both Frederick the Great and Napoleon each fought their own Battle of Dresden. Both had the same opponent at Dresden, ie, Austria.

From Dresden if you are thinking about day trips (aside from Colditz), I heartily suggest Weimar (the town of Goethe and Schiller, if you're into German lit), Görlitz if you saw "Grand Budapest Hotel" and for more history, the town of Bautzen for its Napoleon connection and for its role in WW2 in 1945. There is a war memorial plaque (Gedenktafel) in Bautzen.

Meissen is well worth it, be prepared to walk in the Altstadt, very interesting with the various churches. Meissen suffered little war damage. Pilnitz is well known for its Schloss (chateau). In 1992 I saw the Schloss as part of a city tour of Dresden from Berlin. After twenty-five years I am sure that restoration and refurbishing makes the Schloss even more attractive. The Schloss is the site in terms of your historical interest where the Austrian Emperor and Prussian King drew up what is called in English, the Declaration of Pillnitz, aimed at France.

I love pretty towns, and the architecture in Görlitz (heavily half-timbered with a side of art nouveau) is fabulous. Some trains make the run in less than 1-1/2 hours.

Buchenwald Concentration Camp is right outside Weimar and accessible by public bus. Very interesting explanatory material extends to the postwar period when enemies of the communist regime were confined there.

The handsome university city of Erfurt is very near Weimar. Highly recommended if you somehow don't manage to get to Görlitz.

I note, however, that even with a car it's 2 hours from Dresden to Weimar, really pushing it when the site at the end of the trip is not quick to visit. I stayed in Erfurt and day tripped to Weimar from there.

The tourist office in Dresden runs a city walking tour that I enjoyed. I also loved the Historic Green Vault (timed ticket required), which is chock full of objects that are either gorgeous or overdone, depending on your point of view.

Alas, I haven't been to any of the your other destinations, so I cannot compare their desirability to the places I've suggested.

Near Dresden on the way to Bautzen, there is the town of Radeberg, known for its brewery, assuming you're interested in beer. In the Cold War days, Radeberger beer was considered the "best" made in East Germany, "DDR Bier."

Stolpen (bus) OR Moritzburg (steam train from Radebeul) - both have castles - which would be more interesting?

Moritzburg is more picturesque and great for photos, but I would still recommend Königstein fortress instead.
PS: and if you visit Königstein fortress don't use the elevator but enter the fortress through the main gate, the most vulnerable part of the structure. IMHO that's the most interesting feature of the fortress.

Pirna (Sonnenstein Fortress, museum on the the Nazi euthanasia
program), OR Colditz (castle where British prisoners escaped) Which
would be more interesting?

Colditz as a castle is more impressive, and they offer more in terms of WW2 stuff. But the old town of Pirna is quite nice, and the town church has a nice interior.

If we did rent a car for the day, could we combine Meissen and Colditz
or is there a better combination?

It's possible, but keep in mind that Meissen, with the castle, the cathedral, the old town and the porcelain manufacture, will take some time, so I guess you can't see everything.
As a alternative you could combine Colditz with Saxonys most beautiful castle: Kriebstein. This area is actually full of castles.

Radebeul (wineries) OR Leipzig

Depends on your interests. For a relaxed day you could hike from the Renaissance summer house Hoflößnitz (beautiful interior) through the vineyards to Wackerbarth castle, which has a good shop. Radebeul itself is a small town with many posh villas, but there is also a old wine village called Altkötzschenbroda, which offers many cozy restaurants.
Leipzig on the other hand is a big city and feels a bit like Berlin in small. It's also called "Hypezig" because it became quite popular among hipsters...

Any thoughts would be MOST appreciated!!!

Well, I know you can't see everything, but I miss three regions in your list: Upper Lusatia, the Ore mountains, and Saxon Switzerland. To me these are the highlights of Saxony.

Upper Lusatia is the region between Dresden and the Polish border. It was part of Bohemia (todays Czech Republic) for a long time and is culturally not really Saxon. It also houses a small Slavic minority around Bautzen, the Sorbs, and in the eastern part around Görlitz you can encounter many Silesian traditions (Görlitz was part of the Prussian province of Silesia, and after WW2 Silesia fell to Poland and many of the expelled German inhabitants settled around Görlitz).
Both Bautzen and Görlitz are highly recommend. Bautzen is a Baroque town surrounded by medieval fortification and the cultural capital of the Sorbs, and Görlitz with more than 4.000 listed buildings is simply one of Germanys most beautiful towns.

The Ore mountains were once the richest part of Saxony, and the area deleveloped a very unique culture. Basically everything there is related to mining, and even in small villages you sometimes find two or three visitor mines. The mountains are moreover Germanys Christmas country, since many of the traditions were born there.
I would recommend to see at least Freiberg, a beautiful preserved miners town, once the richest town of Saxony, and if possible Seiffen, a village deep in the mountains with nothing but Christmas shops all year round.

And Saxon (and Bohemian) Switzerland is a must. These are simply the most picturesque mountains of Central Europe.

Martin, thank you so very much! Germany has so many treasures that we simply must plan another trip - and then another!

(fortunately, we're now retired and have the time:)). Over the years, we've learned that it's much nicer to pace ourselves and enjoy the place. After all, it's the European lifestyle we appreciate) - a walk, a museum, a lovely lunch - than racing thru museums we won't remember two weeks later and so your suggestions are hugely helpful

Konigstein has been added, Moritzburg and Leipzig subtracted, Colditz/Kreibstein highlighted as a possible 'maybe' if I can work thru the transportation. The day in Radebeul sounds lovely - but I've not been able to find any information on Altkötzschenbroda on the internet in English. Is it walkable from Radebeul or is there public transport? A cozy restaurant after a day walking the vineyards would be great way to end the day.

Again, many thanks!!

The suggestion of going to the Buchenwald camp can be easily done from Weimar. Walk straight down from the Weimar train station to Goethe Platz ca 25 mins to catch the bus. Goethe Platz is a major stop where numerous bus lines converge.

I haven't been to Stolpen, but the Schloss in Moritzburg is magnificent, at least from the outside. There was a "special exhibit" in Moritzburg the day I visited which mostly covered up the normal interior decorations, so I'm not sure what it usually looks like.