Did you try http://www.busuu.com? I don’t know any software. There are many programs for all platforms to do vocabulary cards ;)

You could try www.byki.com, it’s free. Rosetta Stone seems good, but I only have the demo. I use books, but that doesn’t really help with pronunciation and your accent. After I was able to hold a conversation, I started going to www.elchat.com to practice with natives from other countries and get them to teach me slang and local expressions.

Buena suerte ;)

Supermemo.net for learning vocab with spaced repetition—awesome and free. The iPhone app is brilliant.

www.busuu.com for vocab
www.livemocha.com for making friends with whom you can chat, and getting recorded and written exercises reviewed by native-speakers.

Not “software” as such, but audio from Michel Thomas and Learn Spanish Like Crazy

I’ve only ever heard bad things about Rosetta Stone, and it’s crazily expensive.