Whenever I feel like going out at night, doing some culture thing and I do not know what or cannot decide, I check out jlbjlt.net. Concerts, exhibition openings, projections, theatre, performances, dance, workshops – jlbjlt.net is my virtual spot, where I always find something interesting.
All events are well described, I can filter them by choosing a city (e. g. Prague) or the kind of event I feel like (dance, exhibition, etc). Each event is often accompanied by a downloadable invitation or flyer, you can link it with your iCal, Facebook (fcbk) or by clicking on the gmap link you will find the given place on … yes, Google maps :).
So when in Prague, support a culture of marginal interest, but of considerable importance!