i-GO

I started out using TomTom, but had a series of horrendous navigation experiences (it sent me down dirt roads, wayward routes, private roads, no through roads etc.), and have recently been trying out i-GO, which, apart from slightly dodgier voice prompts, works a treat. Highly recommended.

It involves a couple o workaround to get it to work fromt he internal storage, but these are well documented at xda-developers.com

Co Pilot or Garmin Mobile XT

Both use the same maps and have a very similar interface, CoPilot is a little more expensive but is also more extensive.

I'm very happy with Garmin Mobile XT which is running on my SPV M700 however i'm not sure if it would suit the Diamond as it comes on an SD Card....

TomTom is ok, but i don't find it as accurate as the others and it seems to slow my handset down a lot (probably less of an issue on the Diamond mind!)

Amazon are pretty cheap for both, or were when i last looked.... the CoPilot maps with European maps built in are very difficult to come by (one of the reasons i ended up with the Garmin software)

Diamond GPS Software

You can use a number of software programmes, CoPilot Live 7 or TomTom both work. All you need to do is copy it to the internal memory of the machine.

It will then operate as if it was a memory card in the machine.

I am using TomTom, but theoretically CoPilot is the more advanced software. You can get either one from any good online retailer.