If you have to itemize all of your expenses while you're in the field, there's a new portable scanner with OCR/database software designed especially for scanning and itemizing receipts: http://www.neatreceipts.com/.
It's PC-only so I haven't had the opportunity to test it. But if it works as it promises, it would be fantastic. I'd be the first on the block to get it if it came with Mac OSX software (I've written to them requesting it). And it would also be great if it had the option of ditching the scanner and allowing us to image our receipts using our digital cameras. The software would still be responsible for OCRing the receipts, entering the item categories and amounts, and managing the database.
