Wallearn is a neat little program that allows you to learn "subconsciously", in all the tiny little snippets of spare time you have every day. It works by using your Windows desktop wallpaper to display digital flashcards, which it calls pages, which come packaged in collections called "courses". You don't sit there and view the pages, you just glimpse them occasionally as you close and open windows and generally go about your work on the computer. This sounds silly, but I've been using it for a while and it's amazing how much down-time you actually have, and would otherwise just spend staring blankly at your desktop. Of course, this is only true if, like me, you spend at least 6-8 hours every day at your computer.
The only problem with Wallearn is that there are very few courses for it, and making them is a bit tricky. If I ever had any free time, I might make a tool to do it, but don't hold your breath. In the meantime, I've made a small 10-page course to help me revise my French, and I may make some more soon.