this new player looks pretty cool, check it out below. Don't know if it works on 6600, had to post pretty quickly. Its 25 euros. I tanslated it into english for you. I reckon that on the ngage its better than mobiclip and pvplayer because the quality is pretty good, the file sizes are quite small.
Actually heres a working link, but its in german. Also, i looked again and it says it plays rubbish on the 6600