Consisting of a sleek little scanner and some proprietary software, NEAT Receipts for Mac Advance Release is a complete solution for capturing all of life's little expenses automatically. You scan a receipt, and OCR software captures the vendor, price, sales tax, and other data into a library along with an image of the receipt.
NEAT Receipts for Mac Advance Release doesn't have all of the features of the PC version yet, but it will when the final version is released in January, 2009. For the time being, you can buy the scanner and software for $179.95 (a full $50 less than the PC version) and upgrade to the full Mac version for free when it ships.
Thanks to Rachel for the tip!