It's good for any one single item until midnight tonight. I'm not sure if they sent it to everyone or not. I haven't bought much recently, so maybe that's why I got one. It looks like it is tracked to your eBay account to make sure you only used it once, so perhaps it won't work if you didn't get the email. Here are the instructions that came with my email:

"Here's how to redeem this coupon:
1. Start shopping on eBay. Be sure the seller accepts PayPal.
2. Pay for your item with PayPal before the expiration date (November 30, 2008). Make sure the
email address on your eBay account is also on your PayPal account. Find out how.
3. Enter code: CHOLIDAYNOV2008

Terms & Conditions
The offer will expire at 11:59:59 PM PT on November 30, 2008. Receive 10% off (maximum discount of $100) the purchase price (excluding shipping, handling, and taxes) of a single item on eBay.com. Recipients of the coupon must be registered eBay members and pay for the item with PayPal.

The coupon is non-transferable, void where prohibited, not redeemable for cash, for one-time use only, and has no face value. The coupon is subject to U.S. laws and cannot be combined with any other coupon. eBay reserves the right to cancel, amend, or revoke the coupon at any time. Use of automated devices or programs to redeem the coupon is prohibited.

Purchases made through any customized checkout system and/or eBay Live Auctions are excluded."