iPhone only: Anyone with a smartphone has been there: You're browsing on your computer but want to transfer a bit of info to your phone. You could email it to yourself, or you could try Pastefire, a clever desktop-to-iPhone sharing tool.
Once you've downloaded it to your desktop, head to the Copy Zone, enter in any bit of text along with a username and password (doing this once will create an account for you — the site's a little annoyingly unclear about registration, but this is the process). Then open up Pastefire on your iPhone or iPod touch and enter in the same username/password. Next time you paste something into the Copy Zone — or, better yet, use the supplied browser bookmarklet to snip some text from your browser — that text will automatically be available when you open up Pastefire.
The most interesting thing about Pastefire isn't that you can transfer text using it — you could just as easily do that by sending an email to yourself. The clever aspect of the app is that it analyses the format of the text you send it, then provides various links to common actions you might want to perform with that text. For example, it might offer to open a link in Safari, send it via email or text message, search for it in Wikipedia, or post with your Twitter client. If you've sent a phone number, it will offer to dial it on your iPhone, via SkypeOut, etc.
The tool isn't perfect, but it's a clever idea for a mobile phone timesaver, and it's a free download from the iTunes App Store.