"tv tuner cleaner" might work... It works for cleaning bad pots so it might clean out the fan. Or it might kill it, I don't know

There are a bunch of aftermarket heatsink and fan units for video cards and you might be able to find one for your card for about $15-$20. The fan on my old GF4 died and I got a replacement that cooled about 15% better (and was a bit quieter) for $20.