What's a good day trip from London?

There are so many.. when are you going.. what month.. obviously a daytrip to Brighton would suck in rainy winter.. but was tons of fun in summer.
Bath is great if you like history...
I liked Warwick Castle.. but had a child with me.. so that was extra fun for him.
Hampton Court was great.. I loved that era of history.
Salisbury is nice to walk around same with Canterbury.

I am sorry.. I found Stonehenge and Stratford on Avon, kind of "meh", but others love it.

What are your interests?

University towns of oxford or cambridge are terrific. Also windsor castle is a fun daytrip. So many terrific places. Hampton court palace is amazing.

Greenwich feels like a day out. The Royal Observatory, the Prime Meridian, an old ship or two. You can get there by tube (faster) or boat on the Thames (slower).

For a bit of country in the city, spend a couple hours walking in Hampstead Heath (by tube).

Both Cambridge and Oxford are easy by train, but you have to choose one.

Take a look at London Walks. They have both day trips out and excellent tours in the city.

I'll be in London from the 12-18th and i'm pretty open to anything (scenery, history, etc). However, I don't want to waste so much time on the transit getting there or if I do, I'd like for it to be really worth it.

As others have said you have a myriad of places to choose from. For me, for lasting impact ...
1) Oxford
2) Bath
3) Stonehenge and Salisbury Cathedral

So many to choose from. A few more for you list:
Cambridge is nice
Some people find Canterbury or Dover nice day trips (the castle and cliffs of Dover are worth a visit).

DJ

I love doing day trips from London by train! So much so that I wrote an article about my favorites for NC's AAA's "Go!" magazine a few years ago. If you are interested in reading it, private message me with your e-mail and I'll send you a copy. But here's a list of my top few:
Windsor, Cardiff Wales, Bath, Stratford-upon-Avon, Winchester, York, Canterbury, Dover, Brighton
All can be done independently by train.

There are many options.
If you mean a day outside London, you might consider going for one of these organized tours combining Windsor, Bath and Stonehenge. Because of the distances, some time is spent in a bus, and it feels a bit rushed once on the spot, but you will have an opportunity to have a lot done in one day.

There are hundreds of possibilities. I think you ought to browse the internet or look through a guidebook to try to narrow down what you want to do. I have no idea what you think would be worth it.

Are you going to be there THIS month? If so, keep in mind the shorter days and potentially shorter open hours in your planning. London sunset 12 Nov at 16:16 and 16:08 on 18 Nov.

If you are interested in Salisbury/Stonehenge, London Walks has a day trip on Sat Nov 14 which I think is in your time frame.

http://www.walks.com/London_Walks_Home/LW_TIMETABLE/default.aspx

Go to the web page, click winter schedule.

BTW, most of the walks I have done with them have been very interesting and fun. I know you have a lot on your list to see, but if you want a different sort of look at London or are interested in a particular theme, you might enjoy doing one. No reservations are needed, you just turn up at the specified place and time and pay the guide.

Don't overlook Paris, 2 hours 25 minutes city center to city center, via the Eurostar. Really cheap round trip tickets go on sale 6 months prior to your travel date and get more expensive, then much more expensive, the longer you wait to purchase them. www.eurostar.com. Take an early train over and a late train back and get a taste of Paris if you haven't been there before.

Emma, I know that you keep going when the sun goes down....I live in NYC and it will be getting dark by 4:30 soon! But when you're planning a trip to see Canterbury and you get side tracked by a fair in Rochester it's very likely you'll arrive with very little time to see the town in daylight. I speak from my sister's experience a number of years ago when she and her husband combined a business trip with some touring. It's not that she didn't get to see Canterbury at all, but they did wish that they had watched the clock a bit more or that the sun had stood still for another hour. :) So, I think it is legitimate to remember when the sun sets when visiting in winter, wherever you go! (And Rochester was attractive as they live in Rochester NY!)

Emma, I know that you keep going when the sun goes down....I live in NYC and it will be getting dark by 4:30 soon! But when you're planning a trip to see Canterbury and you get side tracked by a fair in Rochester it's very likely you'll arrive with very little time to see the town in daylight. I speak from my sister's experience a number of years ago when she and her husband combined a business trip with some touring. It's not that she didn't get to see Canterbury at all, but they did wish that they had watched the clock a bit more or that the sun had stood still for another hour. :) So, I think it is legitimate to remember when the sun sets when visiting in winter, wherever you go! (And Rochester was attractive as they live in Rochester NY!)

I really enjoy visiting Hatfield House near St. Albans. It's a gorgeous stately home and was the place Elizabeth 1st learned she was queen of England. The family still lives in the house and the gardens are quite beautiful. Well worth a day trip!

You could go to Evans Evans London Day Tours and look at their day trip selection. You can also take the trains out to Oxford or Cambridge. Whatever you decide, you will be happy inside or outside of London.

If you're a Harry Potter fan I recommend a trip to the studios where they filmed the movies. It's about 30 minutes by train to Watford Junction then a 10 minute bus ride to the studios.