Twitter’s password blocking hangs on their sleeve. They make a giant list of words available to javascript at the bottom of their signup page. Go ahead, look at the source. It is actually a very nice list and I was both surprised and pleased to find out from blog at divshare.com about it.
Ideally, a password should be difficult to guess, contain a mix of letters, numbers, and symbols, and should not be based on a dictionary word or anything that is associated with you.
A trick I will use is to take the first letters of the lyrics of a nursery rhyme and replace obvious letters with numbers, 3 for E, 4 for A, and the like.