The only other place I've published the game so far is SlideME, and only because I was asked to do so by someone on a forum. Downloads there are not bad though - about 10% compared of the numbers I see on the Market. Don't know how those numbers would be for a for-pay application though; since us non-privileged can't sell games on the Market and the copy protection in Android is a joke, I haven't had much interest in trying this out.
I'm on the exact same situation as you .
Since I can't upload paid applications, and all my "revenue" comes from ads, I just upload them to slideme.org apart from Android Market .
The download rates are roughly the same as you stated : 10% of the Android market .
I recently got an e mail from appslib.com (which is a market directed to their device , the Archos 5) "inviting" me to post my apps there, and I gave it a shot . I got 5% of the Android Market downloads, but as polyclef noted, I don't know if it's worth the time . I spent like 4 hours changing my code to adapt it to their device, and I still have to create a different AndroidManifest for them, because of some dpi issues .
I think my case and strategy's case is worth to post it on SlideMe.org . As for polyclef who already has some successfull apps, and also can post paid apps, I dont think it's worth the time, since you will NOT get 10% of the hundreds of thousands of downloads you have in the Market .
Anyway, apart from SlideME.org, I don't know any other market worth the effort to upload my games .