The man pages are your friend. As VK has already said, www.freebsd.org
Along with the FreeBSD home page, you will likely want to subscribe to their mailing lists to keep up on patches and bug reports.

Aside from that, there are cheat sheets : http://www.mostgraveconcern.com/freebsd/

If you are looking for a good range of help then check these two out :
http://www.onlamp.com/bsd/ and http://1001tutorials.com/freebsd/index.shtml


Regards and good luck.