wikitravel is always one of the sites i visit to get my research going whenever i travel. it is a very useful source of information on the destination(s) i have in mind. it's a nice site to start with if you want general information about the place and which attractions to see.

however, it is usually not complete so i still have to look at other sources. other sites i make sure to visit are tripadvisor and lonely planet's thorntree forum because they are more detailed in some aspects, like how one should avoid taxi scams, tourist touts, updated prices, etc. i also look for travel blogs and get ideas from them. if printed travel guides are available and updated in bookstores, i browse through them if i have time. these travel books are pretty expensive so i simply hang out and read at the store. the information in printed travel guides are very useful and extensive too but the prices of accommodation, transportation, etc may not be very updated so you need to check when the edition was printed.