There are A LOT of excellent clothes hidden on livejournals and tumblrs, so if you are up to it you could spend weeks going through them. Usually one will lead to the next, just follow links they give on original creators of meshes or some texture they used.
I'd start with trapping, skell, and the trade off. From there you should find enough links to keep you busy for the next year or so.
Seems like my most favorite sites to get my custom content has been here, The Sims Resource, Cyjon, Paladin, and More Awesome Than You. There was a tumbler account based on custom-made clothing for Sims 2, where I found this awesome new business suit that I recolored for one of my Sims.
I don't download much custom furniture, textures for build mode, or other stuff like that since I am rather content with Maxis stuff and I can recolor them myself if needed. I think the majority of my mods are to omit or fix bits of behavior throughout the game.
Lots of new to me sites, and some others that I've heard of and some I forgot about! Hopefully other people found some goodies too.
Seems like Tumblr is the hottest place to download things right now. Seems like everyone has moved there! I almost forgot to download iCad's recolors, thanks for the reminder. I used to get clothes from All About Style and LlianaSims, but they seem to have gone the way of the dodo.
My download folder is not going to like me after this.
I always go through intending to de-fuglify my game and by the time I've finished, I have a bulging downloads folder! Every default links to a page with not only lovely default replacements, but quite often non-default versions, and other content too.
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