There are now two GPU miners released for Primecoin:
1. PrimeGPU has a GPU miner for AMD 7950/280x and up. The cost is 65XPM per GPU. Info on Bitcointalk and Peercointalk.
2. Claymore has released a gpu miner with a 10% developer fee. It is available for download on Mega. Claymore is on the ypool chatbox.
A third developer is looking for a 50BTC bounty for his nVidia miner. His thread is on Peercointalk.