Latvia

We visited all three Baltic countries in 2011 and loved them. They are all very proud of their freedom and independence.
They are all thriving and it is wonderful to see.

We did our trip on a tour that included a Russian River cruise. The tour was via a bus. The roads were generally good, so I would think renting a car is not a bad option. Not sure what tours are available. Also, not sure about rail travel.

We are heading for Tallinn and Riga for Christmas / New Year. Tallinn because the airfare over was reasonable and Riga because there is a $100 flight to Budapest from Riga. Sometimes I travel for pleasure, sometime to see something before it changes and sometimes for political reasons. This hits several of my categories. The region is ripe for "annexation" by Putin so it may be a see it now or never (if it ends up like parts of Georgia, or parts of the Ukraine or parts of Moldova) opportunity. Needless to say I cant imagine myself leaving my money in Russia right now.

A good resource for places formerly behind the Iron Curtain is In Your Pocket. They have info on their website, you can download their guides as PDF's, and you can get the guides on paper for free in the city itself.

Here's their Latvia page for starters: http://www.inyourpocket.com/latvia

This might give you a starting point. We were there in 2012 and liked these hotels--all were moderately-priced and well-located in or near the city center:

Tallinn, Estonia: Go Hotel Shnelli

Riga, Latvia: Old City Boutique Hotel (near the Opera House and we were able to get tickets to the Opera while there); The Occupation Museum and the Art Nouveau Museum were very interesting.

Vilnius, Lithuania: Hotel Domus Maria

We flew into Vilnius. Took a bus to Riga. Bus to Tallinn. From Tallinn we flew to Stockholm and then took a ferry to Helsinki to complete our trip.

For us, it was a great experience!

We've been to Lithuania three times for a month each and also to Tallinn. The RS Scandinavia guidebook has a chapter on Tallinn and I also recommend the In Your Pocket guides. In Vilnius we've stayed at the Domus Maria Hotel a couple of times and agree with the recommendation. We suggest buses for transportation; they were very good (see eurolines.com). In Vilnius there are several cathedrals (with stories of their use during the Soviet era), a KGB museum, a couple of Jewish sites, and more. The TV tower played a role in the Lithuanian independence movement. There is an outdoor folk museum outside of Vilnius toward Kaunas, and the Ninth Fort on the outskirts of Kaunas. Along the road from Vilnius to Riga is the Hill of Crosses, just outside Šiauliai. Can't speak to Riga. The sites in Tallinn are described in the guidebook. Have a great trip.

I'll comment on Lithuania...see Klaipeda, the former town of Memel, the most northeasterly tip of the former East Prussia.

Thank you for all your suggestions. Currently thinking about taking a flight from LAX to Helsinki on Norwegian airline (seems like the best prices at present.. anyone have experience with them?), then taking the ferry to Tallin, and finding some scenic route from there to Riga. Not sure yet if we need to return to Helsinki for the return flight or if we can just go to Stockholm and leave from there..
Would have been nice to see St Petersburg, but the visa hassle may not be worth it..

You don't need a visa to visit St. Petersburg by ferry (see: stpeterline.com) from Helsinki or Tallinn. We've done it and others here have also. Two nights on the ferry plus up to two nights in a St. Petersburg hotel equals a max of three full days in St. Pete. You can purchase through an agent in the US or other countries. If you are interested in St. Petersburg I encourage you to check it out.