What to do in London at night

Hit a local pub and enjoy a few pints or some other beverages

How about the Ceremony of the Keys held every night at the Tower of London. It's free you just have to reserve in advance.

http://www.hrp.org.uk/toweroflondon/whatson/ceremonyofthekeys.aspx

If you like classical music or jazz, you can't go wrong with a concert at St Martin-in-the-Fields. Go here for the October schedule.

What about a London Walk's evening pub tour?
A great way to see part of the city, and after the tour is over you can head back to the favourite pub that you visited for another pint or two.
http://www.walks.com/

We love to just "wander around". We often will walk from Covent Garden, through Leciester Square, down to St. Martin's in the Field, past Trafalger and on to Big Ben and Parliment. Sometimes we even walk down Pall Mall to Buckingham Palace and St. James Park. People watching is fun and Leciester Square, Covent Garden and Trafalger are great places to do just that. The pub idea works well with a walk. Stop whenever you notice a "good" place and indulge in your favorite beverage (soda, ale, or something else)or get a dessert, then wander some more. There are also lots of clubs, if you are into that. Although you have access to lots of shows at home, there are a few that seem unique to London, such as the Reduced Shakespere productions, etc.

You have access to British actors performing in Shakespeare's plays in a recreation of the Globe? Don`t entirely discount seeing a show... you really don't have access to what is in London. I've seen so many amazing shows there that you DON'T get anywhere else - they don't tour, or the production is specific to London with that particular cast.

If you really, really don't want to see a show... some people have enjoyed taking an evening bus tour, or an evening trip in the Eye.

But I really would recommend a show! Even when I'm not there, I keep track of what's currently on, and am bitter about what I can't see (Lenny Henry as Othello!).

I agree with the others re: not discounting the theatre. You could maybe head for the fringe theatres and see something that is edgy, unique and perhaps more authentically British (in that it's not aimed at international tourists). And also cheap BTW!

Or how about comedy clubs? Seeing stand-up comedy in another country can be a great way of getting another insight into the culture.

Otherwise you can try concerts/gigs or see if any of the museums/galleries are having an evening event.

Why not bookmark the Time Out in London site and check it out just before you travel?

http://www.timeout.com/london/

Thanks everyone. Here's another question...Has anyone done the bus tour at night? I'll rethink the shows but I only have 2 evenings there and I'd really like to see more sights.

Another good site to check closer to your time of travel is www.londontown.com.

Another vote for the theatre. LA has nothing on London's West End.

Southbank walk at night is great.

Oxford Street and surrounding shopping district evening window shopping is nice too.

While I can't say if it is any good or not yet, my mom and I are condsidering going to Absolut Icebar London, a bar made of ice.
http://www.belowzerolondon.com/absolut-icebar-london/