Is There Linux Trip-Planning Software?

Spiral Man writes: "There has been a lot of talk lately about Linux on handheld and embeded device. One interest of particular interest to me is in-dash computers for cars. Probably the most important app for one of these (aside from the CD player) would be a navigation and trip planing package such as DeLorme's Street Atlas, and Microsoft's Streets USA. My question is: Are there any apps, or even plans to write apps like this for Linux. Preferably these would use a commercial, or at least well updated, street database, and would have to be able to track you current location with a GPS." Especially considering the coming flood of GNU/Linux-based handhelds and dashboard computers, this question will be one of the toughies for folks who want to use Free software wherever possible, but who also want the capabilities in applications like Streets USA. Are there any competitors out there in the Free world?