Web Worker Daily's got a nice little roundup of apps that allow you to share your clipboard between multiple computers. There's tools for Windows, Mac and -- most useful -- cross-platform.
Also, as a user points out in the comments for the post, there's cl1p.net, a web-based tool that lets you cut-and-paste and share text, files, images and URLs. It's even iPhone ready, which is nice, considering nobody seems to want to put an actual clipboard on the darn thing.
These are all cool tools...but personally, if I need to copy text from one machine to another, I just email it to myself. How about you? Got any other easy tips for moving content across machines?