"ASP page"?? You're in the wrong place, brother ;-)
But seriously... displaying an RTF in the brower may or may not be a piece of cake... depending on how the user's browser is set up. If it's set up to handle the RTF mime type (inline), then displaying the file in the browser would simply be a matter of linking to it.
Barring that, you'd need to send the file with a CFCONTENT header somehow. And being that the RTF format is pretty unique in it's markup... it's not going to simply be a matter of dumping it out in a .CFM page.
Regardless... the HUGE trick is going to be able to get whatever solution you build to save the file back to the server. In order to open it on the client's side, the browser is going to have to download it locally... saving is only going to affect that local copy. There isn't going to be a magic toolbar button or menu item that says "save back to server".
And then the OTHER big trick is going to be coming up with some sort of locking or change management, so that multiple users can't edit the file at once and run the risk of corrupting it, or at the very least overwrite one anothers revisions.
Why is it you're using an RTF? A multi-user database hooked up to a webform would seem to be a solution more suited to web deployment.
-Carl