Taperesources has great prices, and they are wonderful to deal with. Can't recommend them enough.
If price is all you care about, go to www.ecost.com. Got Sony tapes there a few weeks ago for close to $2.00 each. I just checked, and they are back to $3.19 each. Taperesources is $3.99 for the same tape (quantity 5).
Another vote for Tape Resources. They care about their customers, they have awesome service and you are not treated as some random low level peon no matter if you buy 1 tape or 1,000.
The best prices I've seen on the PQ and MQ Panasonic tapes (the MQs are the only tapes I put in my camera), are from http://www.alartvideo.com/tape.html. He also sells the full-size DV tapes well below anywhere I've seen. Great to deal with--recommend highly.