Just FYI,
dipmicro.com has recently started carrying Arduino-compatible boards made by Seeedstudio. It has quite a selection of boards but it's trying to test the water with small stocks. So if you're buying some arduino boards, give them a consideration. Their parts prices are among the lowest I've shopped since 2009. If we give them the right signal that arduino is popular, they may decide to stock more boards and who knows maybe even sensors.
Here is a coupon:
SPRING10
Trust me, it works. All orders above $10 get some shipping discount.
Disclaimer: I'm not related to dipmicro.com except that it carries a couple of my arduino shield designs, so do some other online stores. They're small business compared with sparkfun.com but quality of parts makes no difference as far as I could tell. If you like them, spread the word. They could use some word-of-mouth ads. during this bad economic situation.