However, AM2 is not long for this world either. The new AMD processors (a year off) will be "AM3" processors. The current info is that they should work in AM2 sockets, but with their new features inactivated. That doesn't strike me as a very attractive upgrade path. Plus, right now there is no guarantee of this partial compatability. Remember that Core2Duo processors are compatible with the same LGA775 socket as Pentium 4s, but it turns out that their power requirements were different enough that no pre-C2D LGA775 boards could work with C2D processors.
If you need a board that will work with CPUs 2 or more years into the future, you're stuck with current C2D-compatible Intel LGA775 boards. If you don't want to go Intel, go with AM2 for the increased performance, not for any expectation of longevity. Until very recently, AM2 CPUs were priced higher than socket 939 CPUs, but since last week the price difference has gone away, so don't pay a premium for AM2 CPUs.
Finallly, you don't need a credit card to buy online. NewEgg accepts PayPal, personal checks, money orders, etc (of course, you need to prepay on those), and so do a number of other internet vendors.