The best resource for the game is the FarmVille Forum. There is a wealth of information there and if you can't find an answer you can post a question. Always look for a thread related to the subject of your question and post in there before starting a new thread, Redundent threads usually get moved or deleted or are quickly buried in the forum minimizing your chances of getting the answer you seek.
Forum Links
FarmVille FAQ This thread will answer many common questions.
Game Guide This thread has a brief guide on how to play the game. Also check the Help & Support tab on the Menu at the top of the game page for more information.
How to submit a ticket to Zynga Support
Spreadsheets
These spreadsheets are full of useful data on the game. Most are up to date with the current game information. If you have one or know of a good one send me the link and I'll post it here.
Daisygirl's Spreadsheet I used this for some of the data on the Farnville facts page.
7thson's Spreadsheet Spreadsheet showing the time remaining on crop based on % ripe.
Crops Profit Scheme Created by Fred i Dalen.
Crop ROI A contribution by metahuman.
Crop Harvest Spreadsheet A spreadsheet by turtleboyollek.
Other Sites for Information
FarmVille Freaks Blog A lot of good information here about the game.
Other Sites of Interest
FarmVille.com The FarmVille site.
FarmSitting An amazing concept of having your farm tended while away or unable to tend you farm
Farm Report This program runs on your PC and will let you know when your crops are ready for harvest.