Looking for Vocabulary Trainer

Hi guys,

even though I'm presently staying in an English-speaking country and mu English may be sufficient enough to cope with conversations and academic activities, I'd like to improve my vocabulary to gain more self-esteem and to be a better communicator.

I went through all the posts in this forum and I knew the program "Vocaboly" before, but it doesn't really satisfy me, even though it is an excellent piece of software.
The reason for me to not like Vocaboly is that it just randomly asks you words that don't belong to any particular "theme" of words. And furthermore I does not only ask you random words without any link to a particular topic you could like concentrate on and refer to it also doesn't allow you to randomize the list of the words which results in a whole bunch of words that begin with say "ab-" that you would like to memorize. But I somehow can't cope with like 20 words all starting with "ab-" efficiently.

So I hope you guys know what I'm trying to say here...because it's late at night already.

Well, anyways if anyone knows an English-English vocabulary trainer that actually works and is for free that I'd be more than happy to get to know about it.

Thanks a lot in advance