CrossRoads:
I've been using iteadstudio and buying 10, 20, 50 boards.
5cm x 5cm, $9.90
10cm x 10cm, $24.90
I second Iteadstudio. I've used them twice now and been happy on both occasions. To maximise yield I used more conservative design rules than the 8/8 mil they recommend. Rounded corners and cut-outs are supported.