Here is a vocabulary test I tried out, and was surprised at how well I did: Test Your Vocabulary. You get two lists of words- the first tests your broad vocabulary level, with words like; the second your narrow vocabulary. I am in the 45th percentile for adults over 18 years, with a vocab of around 26,000 words. I did not think I was that verbal.
How well can you do? Try it, then come back and brag about (or humbly admit) your score.
HT: First Thoughts blog