There are a few taboos in fiction writing, but you hear a lot about how you should avoid the dreaded Info-Dump (and adjectives. I hate them so much!)
It's handled well, and it's handled pretty poorly. A popular method is the ignorant outsider. In the one Jim Butcher book I read, )Small Favor, from the Dresdon Files), I thought that the explain-it-to-the-outsider scene came off very well. However, when I read several Sherlock Holmes stories in a row, I got a little tired of Dr. Watson saying “Why Holmes, however did you figure it out?” It seemed to be his only function.
Another instance I enjoyed was (you guessed it) from The Empire Strikes Back. Early on, Han Solo mentions that he had to leave because of a bounty hunter he had run into. A colorful history is alluded to linking the first movie to the second, with a single line.
Another good example is in Tombstone, the Wyatt Earp movie with Kurt Russell. Arriving in a new town, the local law enforcement tries to recruit him (showing his well-regarded reputation) and he quickly and flatly declines, showing how tired he is of law enforcement.
How have you seen info dumps done well? How about not so well?