The newest one today is this one...
http://www.reefermagnets.com/trainers/prog/nfsmw/NFSMW_Trnv071-C.zip

- Download zip
- Extract entire zip to anywhere you like.
- Run the EXE
- At this point, you can check mark the cheats you want to enable. The only two that you can't do this with are money and camera view. For money, the profile must be loaded in the game, at which point you just click 'set' on the trainer. For camera view, hotkeys have been added. F5 to cycle camera view forward. F6 to cycle camera view back. (*Note* This unlocks 4 other camera views that are not given to you normally).
- Click the "Play Need For Speed - Most Wanted" button.

The F3 Button:
I have implemented a new way to mass activate/deactivate a chosen list of cheats. Observe in the following screenshot.



Whatever cheat numbers you put in the text bar, are the ones that will be activated/deactivated when you press F3. The list will save between uses as well.

*Edit*

To answer your question directly: Yes, the game must be running in order for the cheats to actually do anything.

-------------------
Beta test the new NFS-MW BE v1.3 Trainer, and/or enjoy the Black & White 2 Trainer.
http://www.ReeferMagnets.com/trainers