I use Excel. I set up a spreadsheet for expenses like lodging and travel, and another for hours spent on various contracts. I made an invoice template in Excel and I transfer the hours and dollars to that twice a month. I also use Documents to Go on my PDA. That allows me to transfer the spreadsheets back and forth from laptop to PDA.
I also belive that either Macworld magazine or Consumer Reports recently did an article on personal financing software (2 issues ago I think). It was a very helpful article. I'll look for it later. Does anyone know off-hand if it was Macworld or Consumer Reports?