APRS.FI This is a global APRS database.

GRLevel3 A Windows viewer for live NEXRAD Level III data.

NWS Shape Files  This will allow you to view the watches and warnings as they get to you via the internet or RF. Warning, it is an 18 meg download so give it some time.

Xastir A Linux version of APRS software.

UI-View.

plugin source for UI-View.