Which order do most (any) producers of rap/hip-hop work? Do they lay down the beat first, or work around the MC?

don't know how others have done it but on the few tracks ive made ive got a mc to put lyrics on my beats and then slighly adapt the track as it starts to take shape

I think it's like a mix of what you say, samuel. It depends of how big the artist is, I think. 50 Cent can choose witch beat he wants but an unknown undergroud artist have to use the beat he is given. But nearly always the artist and the producer have to work together to get a good result.

I don't believe that there is a definate answer to that question. Myself, being an aspiring music producer would just let the creativity flow as it comes. If the beat is what I'm inspired to compose, than I'll do so; However, if the artist feels passionate and ready about his part, then I'll work around him/her.
In the end, all that really matters is the final composition and its quality. Whatever route you took to get to it doesn't really matter as long as you know that you gave it your best.

Yes, yes i know it sounds like motivational speech, but o' well.

Interesting replies... I've always wondered how the artists integrated their talent and thought it was this way. Sometimes you hear some good simple beats and go "I can do that till the cows come home...", but then you wake up and realise how it must really be (i.e. ).