If you run an eBay storefront, or even if you sell only the occasional item, the eBay Mobile
iPhone app will come in handy. With it you can check item prices or place bids on auctions, as well as answer buyers’ questions on the go.
eBay says improvements are on the way; soon you'll be able to create auctions (using images you've taken with your iPhone) and process payments.
A good companion application for eBay Mobile is the eBay Profit Calculator
app ($0.99), which can help you determine your estimated total profit after eBay’s fees, based on the type of auction, the category, and your prices.