"Google Maps [...] built on the native Symbian C++ [...] available for S60 3rd Edition on Symbian OS."Google Maps also includes versions with GPS support for the BlackBerry 8800 and Helio Ocean.
Talking about Symbian, Nokia has a Sports Tracker software package for S60 v3.0 and 3.1 phones.
Microsoft Research has some free mapping apps available for download like the WWMX GPS Track Downloader.
Want to blog from a PDA? Check Mobile Blogger for Windows Mobile: "Read what you like and blog what you think". First on Solsie
Live Tracking? Try Hipoqih.
Want a tracking app for your Nextel GPS phone? Check the Gadgeteer.
Remember Twitter? Here is a J2ME version.