I took some German at the local university (although 3 hours at night after work is painful).

My boyfriend who is from Vienna (although if he had his chose I'd take Viennese German instead of German ), downloaded the "Tell Me More" German program which is less expensive than Rosetta Stone, but the navigation isn't too great.

I would recommend taking classes so you're put on the spot about the grammar and forced to write sentences, etc. The post someone wrote about conversing over Skype with a tutor is a great idea or even find a pen pal online that wants to learn English. Luckily for me I'm exposed to it all the time with boyfriend's family-although I have to admit it's embarrassing to attempt to speak.

In parallel with classes I use a program called Linkword. It's not a good interface, but it's excellent in building vocabulary. It uses "links" to help you remember like "the lobster has a sense of humor", "der hummer". I've found it helpful and it's pretty affordable.

http://www.linkwordlanguages.com/german.htm

I even bought some children stories on amazon in German, Der kleine Prinz is cute. You can also buy short stories in English and German and supplement with those as well.

Viel Spass!