I read a good entry over at Signal V. Noise about how to go paperless by using an expensive duplex scanner from Fujitsu. While I still think this is a great way to do it, and I may even buy one of those scanners, a while back I came up with an easier and far cheaper way to scan my mail and documents into a digital form and have been using it for a while.
Most offices, like mine, have fax machines or fax copiers. I also have a fax to email service through my toll-free provider, Ring Central, where your fax documents are scanned and emailed to you as PDF attachments. If I ever want to archive a paper document into a digital form, I just fax it to myself and save the PDF to my computer. I also leave a copy in my gmail account where I can access the file from anywhere.
The only downside I have discovered is that the faxed PDF is not transformed into indexable text via OCR (optical character recognition) during the scanning process. I compensate for this shortcoming by giving each document a readily comprehensible file name. If you fax each document at a high enough resolution you may be able to perform OCR on the output, however the descriptive file naming used in conjunction with Google Desktop Search has worked well for me.