Hi Kathy, I like the Olympus DSS format the best. It creates the smallest and clearest files and any player on the market will play DSS. A DSS file takes up about 50k per minute of dictation. Most e-mail boxes will hold at least 3000k (3 mb) at a time. That gives you a capacity of 60 minutes of dictation every time you check your e-mail. If you leave your e-mail on all day and have it set to check every 10-15 minutes it will never fill up, unless someone sends you an e-mail bigger than 3 megabytes.
There are many WAV player vendors. Here's a list and some links to check out, in addition to the one Bill provided. All of these play DSS files and more. Most, if not all, handhelds come with software to convert their compressed proprietary files to WAV format.
ExpressScribe at http://www.nch.com.au/scribe/ is free. You have to buy the footpedal. There is a list of the file types it plays at the page above. According to the page it also works with Sony handhelds...
WAVPlayer at http://www.bytescribe.com costs $149 and comes with a serial footpedal. Again, a list of file formats is available from the WAVPlayer page.
GearPlayer at http://www.transcriptiongear.com/products/gearplayer/ has a downloadable demo. Costs $169 with a serial footpedal.
Start/Stop is another popular one. It can be found at: http://www.startstop.com/Transcription.htm it costs $199.
There are many encryption/transfer options available to you. Hypersend is one and I hear it's quite good. PGP is the most popular encryption program, and it's free. There are many other good encryption programs that are free and some that are not. I've written an encryption program also, if you're interested. It does some things the others don't, but it's not free. 
I hope this information is helpful to you in your search for the ultimate digital dictation system. 
Mike DeTuri
[ 10-22-2002: Message edited by: Mike ]