Yahoo has released two products that have come out of its Hack Days: Shop By Color which lets you use Yahoo Shopping to find products matching colors, and MapMixer, which allows you to layer your own maps over Yahoo Maps.
You’ll find Shop By Color at Yahoo Shopping. Do a search, such as for ties, then use the new color box in the left-hand column to a particular color. Here, now you’ve got orange ties. Excuse me, "coral" ties. Interesting feature, though Yahoo’s not the pioneer here. ShopWiki rolled out shop by color back in June 2006.
Yahoo MapMixer allows you to blend your own custom layers or layers made by others onto Yahoo Maps. People have long made these types of mashups in particular for Google Maps, so MapMixer should help encourage the same for Yahoo. Of course, back in July, Google got behind mashups by allowing "Mapplet" integration. You can find a list of Google mashups here, similar to how Yahoo now has its own gallery.
Techmeme has a nice roundup of various people kicking the tires on both tools more.