I've been using Yahoo! Local a lot recently for finding local businesses and restaurants. Sending links to friends, however, is a bit painful because the URLs are so long (and tend to break in email clients).
To make this a little bit easier, I created a bookmarklet that strips the URL down to just the minimum fields, suitable for sending by email. I've confirmed this works with IE 6.0 and Firefox 1.0.4 on Windows, but haven't had a chance to test on a Mac yet and have heard it works fine with Safari 2.0 / Mac OS X.
To install, drag the following link to your browsers' toolbar: Y!Local Send
Update: I tweaked the bookmarklet to work correctly with IE6 on Windows XP Service Pack 2. If dragging the link to IE toolbar doesn't work, right-click on the link and choose Add to Favorites, answer Yes to the warning, then select the Links folder.
Update 2005-07-14: I tweaked the bookmarklet again because it seems that Yahoo! Local changed a parameter for the "details" results.
The latest tweets from 
Works on Safari 2.0.
http://local.yahoo.com/details?city=Austin&state=TX&id=19404062
is much nicer than
http://local.yahoo.com/details;_ylt=Av9w9IyJlFrUXVf.NpAj3XqHNcIF;_ylu=X3oDMTBpZzIyMjd0BF9zAzk2NjEzNzY5BHNlYwNzcg--?stx=thundercloud&csz=Austin%2C+TX+78732&city=Austin&state=TX&fr=&uzip=78732&ed=tvo3Aa131DxHeWphFv3FtJRkz5w8zGmrJwmpNirXsOVriOrEz0I-&id=19404062&lcscb=7kzrz8hxGnb
There is already a service that does this called TinyURL (http://tinyurl.com/). It has an IE Bookmarklet, and an extension for Firefox (http://extensionroom.mozdev.org/more-info/tinyurl).
Most importantly, it works with any URLs, not just Yahoo Local.
works like a charm. thanks!
I also use TinyURL for certain things, but sometimes I prefer to show the actual URL that I'm passing around. Certainly TinyURL has the advantage that Seth mentioned of working everywhere.
Seemed to fail for the following example; using Mozilla 1.7.2 on Linux.
Here is the real (& real ugly) URL:
http://local.yahoo.com/details;_ylt=AlLFu2oPDweKsZJIdtOF4uuHNcIF;_ylu=X3oDMTBpZzIyMjd0BF9zAzk2NjEzNzY5BHNlYwNzcg--?stx=fred&csz=Pasadena%2C+CA+91101&city=Pasadena&state=CA&fr=&uzip=91101&ed=7qyAFa131DyA_grYmNHWs3QLv1v0DFg4e_Jhy83xm4Z8_IGPXg--&id=20609443&lcscb=BZzocRHqBCn
here is the suggested shortened URL:
http://local.yahoo.com/details?city=Pasadena
which is certainly too generic, and in any case actually gives an error: "Sorry, we've encountered an error..."