I used to use firewallet. It was pretty nice. You've gotta set up categories and stuff and manually input everything. I switched to mint because I don't use cash very often and it pulls in my account transactions autonatically, but firewallet was very handy.
Try My Mileage by Michanima. It will automatically track mileage when you charge your phone in the car. It will also scan receipts. Information is saved to SD card and can be emailed off the device. Everything you need for expense tracking. see michanima.com or search com.leptron.mymileage in the Android Market
Well I am the developer of My Mileage Pro. I think it is a great product that people searching for an application to track expenses will appreciate knowing about.