eBay is challenging all you developers there to develop cool applications using their now free web services API.
The ideas listed by ebay looked pretty interesting:
Category/vertical search (re-mix eBay to help people find things more efficiently)
drag & drop UI components for search results page: Offer eBay user the ability to customize their UI for the features they want to use
item ticker/screensaver for eBay
search for eBay items widget
widgets or gadgets
toolbar-like mini-apps
calendar view of members’ eBay activities
auto-Add to Watch List: Allow members to specify advanced search criteria that automatically adds items to their Watch List
low-priced items portal that allows free listing
search personalization
search for eBay items over IM
seller tool to add streaming video to their listings
taxation invoicing tool for eBay sellers
eBay Motors: Find vehicles locally
eBay Motors: Find similar types of vehicle (search for Accord, also show Camry; search for one minivan, see others with more listings)
eBay Motors: Show vehicles and their corresponding Parts & Accessories in compelling layout
Web mash-up (re-mix eBay with another Web service)eBay Motors: historical pricing data (e.g. show Kelly Blue Book prices along with listings pricing)
eBay Motors: Show consumer reports or government safety ratings along with vehicle listings
Search across multiple shopping sites (Froogle/Yahoo Shopping/Amazon, etc.)
Multi-platform (integrate eBay with PayPal, Skype, Outlook, GNOME, TiVo, etc.) applicationsintegrate with POS systems to deliver full inventory tracking for our seller’s online and offline world
VoIP enabled Ask Seller a Question
accounting package plug-ins: Quicken/Quickbooks for eBay sellers
Firefox plug-ins
demographics targeter: sellers can enter in target buyer demographics and receive recommendations on start and end time/auction duration, etc.
Apple Dashboard widget
lister application written on Mozilla in XUL and AJAX
eBay Affiliate Editor Kit Flash Ad module
eBay Alerts enabled on Skype