Def Tech:
In-Wall/In-Ceiling Speakers | Definitive Technology®
Boston Acoustics:
Pasting that exact link fails, so go to
Boston Acoustics PAGES and click home audio/in-ceiling
If you wanted in-walls, there are even more options. In ceiling is more limited.
For home theater applications, get the best you can afford, don't cheap out on the subwoofer. Careful with positioning, make sure the mail seats are well covered by the tweeters.
For background distributed audio only, I've usually specified MUCH cheaper speakers, typically about $90/pair list. For that application more cheaper speakers is better than a couple of expensive ones.
Using an auto-EQ system like Audyssey is essential with all in-wall/in-ceiling speakers, especially the low and mid-priced ones.