Learning Latin

http://nodictionaries.com
YOU NEED THIS!  View classical texts with interlinear vocabulary help.  The best part: you can input any Latin text and it will generate dictionary entries for as many or as few of the words as you want.  It feels like cheating, but it isn't!       
http://yle.fi/radio1/tiede/nuntii_latini/
read (and even listen to) breaking news in Latin!  hey, those Finns have to keep warm somehow!

Classical Texts 

http://www.thelatinlibrary.com
a great online collection of Latin texts (Classical and Christian)

http://www.hs-augsburg.de/~harsch/augusta.html
a greater online collection of Latin, Greek, German, even Yiddish texts of all periods.

http://www.perseus.tufts.edu/hopper/
online collection of primary and secondary resources for Latin, Greek, and other languages.  texts are hyperlinked to dictionary and commentary entries.

General Language

http://www.etymonline.com
learn the provenance and root meaning of just about any English word you could think of.