Welcome to ET.com. There are a few different options available to you, depending on what exactly it is you're trying to do.
If you're just looking for a way for your info to be backed up to your computer, you should look into a good backup app, like
Resco Backup (there are others, but that's the one I use), which will back up all your Treo's data. Your call log and message database are synced to your computer when you actually perform a hotsync, but that's not a good method of maintaining your data.
You could export the info into a memo or an Excel spreadsheet, if you just want a visual record of the data.
If you truly want some sort of interface, there are apps out there, such as
Comet's Desktop Edition and
Treodesktop (there are others, as well) which may suit your needs.