Snagly is a price tracker for eBay. Paste the link to any ebay.com listing and set the price you'd pay. Snagly checks it every 4 hours through eBay's official API and emails you once when it reaches your target, not on every check.

Each tracked listing gets a price history chart, so you can see whether today's price is actually a good one, or a markup that was "dropped" back a few hours later. CamelCamelCamel and Keepa do this for Amazon; Snagly does it for eBay.

Works in any browser, no extension to install. Out-of-stock listings stay tracked and alert you when they're back. Free during launch with up to 25 listings; 3 stay free forever after. Currently ebay.com (US) only.