Here’s Leo, an online dictionary and much more, including discussions on word use and tables of declinations, conjugation, plurals, etc.
On YouTube, here’s Katja with her Deutsch für Euch channel with more than 50 episodes. She’s a grammarian, and a pretty good looking one at that. Episode 36 is a lot of fun.
Duolingo is a fine online language teaching tool. Give it a try!
Linqapp has a neat idea: This is a iPhone or Android application in which you post messages in German (the language you are trying to learn, of course!); somebody whose native language is German reads and corrects your post; then you return the favor by correcting posts from someone in the world who is trying to learn English.