Computers have turned out to be excellent tools to learn new languages, as you can tell from the many different educational tools you can find for this pupose.
Practiquemos (Spanish for "let's practice") is one of them. This tool comes with a basic menu of exercises covering different areas of the Spanish language, but the good thing is that you can freely download more exercises from the developer's webpage, or even create your own sets. This means that you could use Practiquemos to practive just about any subject.
The program doesn't include any theory. It simply plays the current test question after question, rewarding you with extra points if there's an extra difficulty. You can go over the exercises as many times as you need, depending on your language skills.
Now, the negative side: Practiquemos needs a lot of work on its interface: design is fine but usability is terrible. You can't resize windows properly without losing track of certain buttons. What's more, the program has a strange tendency to resize itself with every new question. Also, be aware that in those exercises where you're required to fill in the gaps, you must copy the whole sentence just as it appears, including the missing word. Otherwise it will count as a mistake. Practiquemos is certainly a nice approach to computer-assisted language learning. However, it still needs a lot of work on its interface and usability.