ounique is my favorite. the full thumb preview with two pics per page that go full sized. plus don is an awesome rep - when i need a different full sized pic, he can make it happen right away. they have massive selection, keyword search, send out i.d. with each set, and reasonable prices.

maxpixels costs more, and isn't as searchable, but they have some awesome niche stuff, and their videos are great - really nice.

worldwidecontent is good for full video scenes. they have a lot of them, all from dvd's, and that is working well for me. their prices are reasonable, and they will search for the type of content you want even if it isn't listed on their site. they rip stiff from dvd's just for me - pretty cool! i.d. only for some of them, though...