I don't right now because 1) I'm not actively looking for more of other people's projects and/or already know where to get them, and 2) I've recently begun (finally) to really focus on my own projects (none of which are quite yet at the stage of calling for that kind of site). I do have a basic site set up for the time when those projects do reach that stage. There's little but contact info on it for now, though.
On the other hand, I have "a zillion" sites/blogs that are set up and devoted to my free-time writing. They aren't to promote either me or my writing, however. They're instead more a matter of organizing existing free-time writing in a way a) makes sense for possible future development, b) incorporates my "agenda as a person" and "agendas as a free-time writer" while attempting to explain to anyone who runs into any of it "what the heck is this mess of miscellaneous writing and other material", and c) aims to make some sense of my purpose and reason for spending my non-"real-work"-hours writing material that is entirely unrelated to writing I do for other people
The stuff I do in my free-time is a weird kind of stuff because a) it's not "just a hobby"; I do write "for money", b) I most often write with the idea of somehow "making (the proverbial) difference in the world", c) I write some things for my own selfish purposes, and d) I write SOME things for personal reasons created within a seriously messed up divorce case to the point where getting some facts "out in public" makes some sense to me. Because of that varied mix of purposes for my online writing, and because I think it's important to let anyone who sees it know where it's coming from; I have those sites that both show actual writing and also attempt to explain any purposes for/context within which it has been done.
It would be a lot less complicated, challenging and generally "weird" to just slap up a professional freelance writing site in the aims of finding new for whom to write; but my online stuff is neither part of my professional endeavors nor "just a hobby without regard for income and/or purpose" either. Basically, I'm muddling with the long-term aim of having some of those non-professional efforts fall into place (or not) under one umbrella of "good use of free time by someone who also happens to write professionally as well".
When the back-burner projects are done I'll promote them for what I think they offer - not me as yet one more freelance writer among millions.