Though it's never going to be cheap, the infamous Soho district should be experienced at least once by visitors and Londoners alike purely because of its history and the fact that it is the historic centre of London nightlife. Lying to the east of Regent's Street and west of Tottenham Court Road with the miriad of bars and restaurants on offer, Soho never fails to pull in the punters on Friday and Saturday nights in particular. The sex shops for which it once was known are now far less prominent with the trendies slowly taking over with up-market bars and restaurants. It remains however a wonderful mix of chic and trashy!
Old Compton Street (formerly known as the High Street) is now the most prominent gay area in London with many bars and shops catering for the gay crowd. The street is also home to a number of adult book stores and entertainment venues as well as The Vintage House; London's largest selection of malt whiskey should you fancy some real quality.
London's Chinatown (just near Leceister Square) is marked by the oriental gates over the street. Gerrard Street continues to offer chinese restaurant after chinese restaurant to local visitors, though if we're honest those that we've tried haven't been the best quality ever.
To taste something different, try Tai on Greek Street. This offers organic vegetarian but also tasty dishes for those who enjoy oriental food. If you get really stuck there are always the usual tried and tested suspects of Pizza Express and All Bar One which offer good food at good prices.
For cost-cutting purposes you may want to try the Moon Under Water pub on Greek Street which offers cut-price beers and spirits. The place doesn't look like much from the outside but is huge inside so is a good place to go in a larger group. If you want more of a Soho-style experience go to the Soho Bar just down the road. This has a late night license and offers quite good deals especialy during happy hour from 5pm until 7pm every day.