Borrow all the most recent books from the library! I prefer Frommer's Italy to the Lonely Planet guide. I found it was much more critical and gave ratings for everything. DK Eyewitness guides are brilliant for focussing on individual attractions so you don't miss anything when you're there.
Useful websites: hostelworld.com, bugeurope.com, www.tripadvisor.com, http://www.travel.dk.com/venice