I got a Melokia solid mahogany concert about 6 months ago from islandstylemusic on eBay and really like it. Plays well and nice mellow tone, and they are about $130 which is a pretty good price for solid wood.
My first decent uke was a Kala KA CG (gloss finish laminated mahogany with white binding) from musicguymic on eBay for about $125 with a case and upgraded strings, set up nicely. I love it and still play it regularly even though now I have some MUCH nicer instruments. It sounds good, looks nice and is really easy to play. http://cgi.ebay.com/KALA-KA-CG-Gloss-Mahogany-Concert-Ukulele-Case-Setup-/250648332916
I haven't played one, but the flamed mahogany ought to be nice too. It's $20 more, but if you like the way it looks... I have a friend who has the tenor version, and it's pretty good.