Here are some eBay related links that will come in handy from time to time. I have also added some other sites that may be of interest.

The world's premiere auction website.
  eBay registration page.
  eBay store registration page.
  List of acronyms used in eBay listings.
  Glossary of eBay terms.
  Icon glossary for "My eBay" page.
  List of eBay auction related fees.
  List of eBay store related fees.
  List of eBay motor related fees.
  Details of eBay's insertion fee credit for relisted items.
  Details on requesting a final value fee credit.
  Procedure for handling non-paying buyers.
  Procedure for mutually removing negative feedback.
  Procedure and requirements for ending your listing early.
  Block unwanted bidders from your auctions.
  Procedure and requirements for retracting a bid.
  Trading assistant directory page.
  eBay's historical completed data service.
  eBay's auction management service.
Provides merchant services for your eBay account.
  Details on PayPal merchant fees.
  Details on PayPal transaction fees for international payments.
A little known secret about Amazon is they have a 30-day price guarantee on items sold directly by Amazon. If the price drops on an item you bought within 30 days, Amazon will credit back the difference if you request it. The price guarantee applies only to the Amazon site. There is no price matching with other websites. To request a credit, use the customer service email form and select "Returns & Refunds" as the issue.
These guys have some of the best prices on the web for computers, peripherals, networking and consumer electronics. They have excellent customer service and their website has a wealth of product reviews. You can spend hours scouring the web trying to find lower prices, but you will discover Newegg consistently offers the lowest, or very near the lowest prices. The only downside is sales tax is charged in CA.
They are one of the largest domain name registrars on the web. They offer $9.99 domain name registration along with a bunch of tools to help you get your website off the ground.
If you are shipping a lot of product with the USPS, you should consider using stamps.com to automate much of the work. Postage can be printed directly from your computer and the status of each package can be tracked very easily. They have a 4 week free trial, so give them a try.
This is one of the largest liquidation sites on the web and it is free to sign up. There is a wide range of merchandise available. New lots come up frequently, so check the site often. Item lots are listed auction style with the highest bidder wining the lot. Before bidding, make sure to read the manifest and look at all of the pictures. Read the fine print. The majority of the auctions are listed as-is and there is no turning back once you make your bid.
Apple Store
Get your Apple products directly from the Apple store. You can get a Mac customized to your exact specifications, iPhones, iPods, iMacs, MacBooks and a variety of other high tech gadgets. Free shipping on orders over $50.
If you have a flexible schedule and can leave on a few days notice, priceline.com is the site for you. Incredible bargains can be found for all sorts of great travel destinations. Airlines need to fill empty seats before the plane leaves, so if you can leave on a moments notice, you can get that seat really cheap. With William Shatner being the front man, how can you go wrong ;-).
One of the premiere travel sites on the internet. You can plan everything from flights, rental cars, hotels and more. They have all sorts of package deals at bargain prices. It is definitely worth checking back once in a while to see what new deals there are.