Thanks to Alex in Year 13 for telling me about this. Interlex is a FREE piece of software, for PCs only, that allows you to input vocabulary you want to learn and then tests you on it. This is what they say about it on their website:
Interlex provides a highly focused, interactive learning environment that allows you to improve your language skills rapidly. Creating your own Interlex files is an excellent way to explore a language and become familiar with new vocabulary. You can then commit this knowledge to long-term memory by testing yourself in a variety of ways. Words and phrases are carefully selected with reference to previous input, encouraging you to concentrate on those you find difficult. Feedback is immediate and informative, without any distracting special effects. The overall result is a tangible sense of progress that makes vocabulary learning a pleasure instead of a chore.
Basically, my opinion is that any way of learning vocabulary is better than doing nothing, but I think this is excellent, and recommend you take a look at it at http://www.vocab.co.uk/.