For general information:

 

www.budapest.hu (the city's official website),

www.budapestinfo.hu/en (Tourist office official website),

www.budapestsun.com (English language Newspaper),

www.budapestweek.com (English Language Newspaper),

www.koncertkalendarium.hu (concert programm),
www.opera.hu (Hungarian Opera with on-line ticket sales),

www.mupa.hu (Palace of Arts, new concert hall),
www.spasbudapest.com/tartalom.php (Thermal Baths in Budapest),

www.spasbudapest.com/tartalom.php (Festivals in Budapest),
www.pestiside.hu (a great, funny website with a lot of infos about
restaurants, pubs, going out, etc),

www.webmap.hu/bp (searchable map of the city),

www.bkv.hu (Public transport in Budapest),
www.kavehazak.hu (Budapest coffe houses, in Hungarian).