American Association of Teachers of German--
This site has links to everything you will ever need!
Great grammar exercises
http://www.interdeutsch.de/studien1.htm
More grammar exercises
http://home9.inet.tele.dk/nkofoed/quiztygram.htm
Even more grammar exercises listed by topic
Diddl Maus Bilder und Karten
http://www.diddl-welt.de/
Diddl: great postcards and pictures
http://www.springmaus.de/
Order Diddl products in the US
http://www.diddlusa.com/
Professional Page