I bought a Seiko 5 from Overstock a month ago (June 2012) and it's a great mechanical watch for the money ($115). BUT its bracelet squeaked. And whenever the watch rides up my wrist, I shimmy my arm to make it slide back down, so I was hearing the squeaking often.
I read some tips--take a shower with it, lube it, etc.--but all of those just treat the symptoms, not the cause. The cause is that when the bracelet is assembled (it's folded and welded, not milled), nobody manually smooths the surfaces that rub together.
The squeaking on mine was coming from the lug links. Here's what I did (sorry, no pics--I never remember to take pics during these procedures):
Buy 400-grit and 600-grit wet/dry sandpaper (the normal black kind, from the hardware store). Remove the bracelet. Using the 400 then the 600, sand the surfaces that touch and rotate (the outsides of the lug links and the inside of the curved link--see the photo). Double the sandpaper over to get better contact. Go vertical then horizontal and CW and CCW. You can even round the edges a little with the 600-grit. You want to make sure there aren't any burred edges. Everything should be almost convex. Don't worry--you won't remove enough metal to loosen the bracelet.
When you finish this, you have to also smooth around the bore holes in the links and the folded metal edge in the curved link. This is so that the lug link won't squeak around the spring pin when it rotates (different than squeaking caused by the links rubbing together). Make little triangles (think little pointy paper airplanes) out of the 600-grit sandpaper and carefully go around the edge of the bore hole at a 45-degree angle. Do the same with any burred edge on the folded metal part of the curved link. Again, the name of the game is to smooth every edge that moves and comes in contact with other metal (pin or link).
After you've got everything smooth, use compressed air (or just blow real hard and close your eyes) and a towel (or your undershirt, like I did) to clean the metal dust off everything. Reattach the bracelet and you should notice much less squeaking. Hope it works for you as well as it did for me!