Roadrunner alerts You about speed cameras.
The Snuggle application uses the cell tower information to locate the geolocation coordinates. It captures the CellID parameters (available from the connected GSM network) and by using Google APIs translates those to locate your position in a map.
NetMon Cellular Network Monitor for Maemo. Displays Signal Strength in dBm, Cell ID, LAC, RNC, Network Code, etc.
The Cleven application is a user interface to the aircrack-ng for the N900 device. It provides the ability to easily configure the injection drivers, scan for surrounding stations, and, using injection and authentication or deauthentication, capture Identification Vector keys. In addition, it provides interfaces to decrypt the captured files and manage the successful attacks.
pymucl is a MUC client for telepathy, especially aimed at Maemo 5. There are MUC clients in the repositories but none of them uses the accounts already available on Maemo.