I will definitely second the recommendation for All About Style. If you're short on time or don't know where to start, try there. They don't have a huge amount of clothes like some of the bigger sites, but all their stuff is well done and tasteful and they have stuff for neglected groups like men and elders. As Blue pointed out, they also have Victorian and other period piece clothing as well.
I think they have a great selection; I also love their accessories section. I love earrings for my Sims, so I definitely "shop" there.
One more thing about these sites - all of them are free (or have free sections).
Thanks for posting that link again, Kingdom. I love that site too