grammar drills at German.net
This site has some really good exercises broken down by specific grammar points, as well as verb conjugation exercises. http://german.net/exercises/
That looks like a really good complement to DL's teaching methods, for those of us who need a bit more drill and a chance to beat on specific concepts and clarify them for ourselves.
Odd that you can't seem to actually create an account and track your exercises.
Thanks for the link!
I just tried this link. It's a great supplemental learning tool. Have a Lingot!