Extensive underground and tramway public system. Here you find the official websites with maps and info: http://www.dpp.cz/en/ Very easy to blackride, no tolls in the metro stations and no drivers who ask for tickets at bus/tramway entrance.
Accommodation & Wild Camping
Hospitality exchange community is pretty well extended.
If the wheather is nice also the parks on the western and southern (hilly) parts of the city are good for wildcamping. 4
Going a bit further you find also national parks like Přírodní park Šárka-Lysolaje.
Shower & swiming
Natural swimming pool Džbán, Hostivar reservoir, Outdoor swimming pool Motol, Biotop Radotín
Local restaurants are quite cheap, with 30-50 czech crowns (1-2€) you can easily have a soup. Dumpsterdiving and freegans opportunities are also good, check http://trashwiki.org/en/Prague. A little rule for going to the restaurants - you shouldn't pay more than 200-250CZK for a meal or more than 50CZK for a 0.5l beer.
There is an official website busking.cz (unfortunately just in Czech) with lots of info about areas, permits etc. Basically there are 3 different kind of areas, one where any street performance is totally forbidden (very few places), another where are forbidden only music performances and then any other place where everything is allowed.
The city centre is always overcrowded with tourists and can make you earn very good money in spite of the cheap cost of life of the country (you could easily make in an hour what an average Czech make in one week).
In the main, touristic square of the old town (Staroměstské náměstí) there is also often (furthermore than dozens of buskers, musicians, performers, etc) a police van with informations and explanations, also in english, about the official laws, policy and regulations.
If you stand on one leg on an advertisement panel playing your instrument, police may come astonished and ask you (after what are you doing so and why..) to come down, check your documents and kindly ask you not to do it anymore.
Update 2016 The busking rules have changed a lot. New forbidden places on the list, new stupid rules about instruments (you can't be too loud and you can't play any high notes) and you can only play every second hour on each side of the river Vltava. Václavské náměstí is still a good spot or you could even try riversides in the evenings and parks if it's really a nice weather. Be aware of policemen or try to kindly ask them where you can play and if you're allowed to play with your set. The situation depends on every officer. A little tip - if you want to change your coins into notes to maybe save space in your wallet, usually smaller cafés beg for change.
A FB group for busking in Czechia - https://www.facebook.com/groups/buskerville/?ref=ts&fref=ts
Bio Oko - A very good and cheap cinema. Usually streams alternative movies but you can catch up basically anything there.
Kino Aero - The same as above.
Vzorkovna - An underground bar located at Národní 11. Regular jam sessions, live music, poetry readings with an interesting local/expat crowd. Everything's possible in this place.
Bajkazyl - A bar/open air music venue located at the riverside (station Karlovo Náměstí, exit to Palackého Náměstí). This place also functions as a bike rental.
Letná - The pendulum is quite a famous landmark of Prague and you should even see it from the Old Town's Square and Pařížská street. The top is the Prague's skaters mekka and a great place to chill in the summer because the view is just stunning. Also, there is finally a bar right under the Metronome with good&cheap drinks and interesting story (ask the staff for that).
Čítárna Unijazz - A classic intellectual café and independent bookstore/reading room. Affordable coffee, homemade soft drinks, good beer. Location - Jindřišská 5, 4th floor.
Ouky Douky Café - A vintage bookshop/café/pub. Cheap drinks and snacks can be found here. Location - Janovského 14.
Holešovice district - Listed as the 15th coolest neighbourhood in Europe. Make sure to grab a drink there or watch a movie in Oko (see above). Start your stroll at Vltavská station and go up the Letná hill.
[http://www.kampushybernska.cz/en/campus-hybernska/ Campus Hybernska[, is a new cultural venue, which many free events.
The activist groups Prazdne Domy regularly promotes available spaces.
Near the Florenc metro statio, locals started renovating a vacant building called Bar/ak[, installing a pottery studio, bar, cafe and community grilling area.
There is a free shop functioning in Klinika (see above)