Drag Chunks of Text onto Dock Icons
Doing this with different applications will produce different results. If the application will accept the text, it will darken when you hold the selection over it. Note that some applications will only accept the text if it is in a certain format (a web address for example). Here are the results with a few common applications. If you know of any more, add them in the comments.
1. Safari - If you drop a web address (i.e. something that starts with http://) on Safari, it will load up that address. If you drag any other bit of text, it will perform a Google Search on it. This is mainly useful if the text is from a non-cocoa app that doesn't have the "Search in Google" item in the right-click context menu.
2. Firefox - If dropped text is a web address, Firefox will load it. This is helpful if you want to view a site in a browser other than your default browser.
3. Mail - A new message will load up with the dropped text as the main message body. Annoyingly the text is placed in the body even if it is an email address.
4. TextEdit - As expected, this loads a new document containing the dropped text.
5. Skype - If the dropped text is a phone number, Skype will call it. This will also work with nicknames in your contact list.
6. Script Editor - A new script window will open up containing the dropped text. Script Editor will then attempt to compile it.
7. iTunes - If you drop a podcast address onto iTunes, it will subscribe to it. If the address isn't a podcast, iTunes will attempt to do it anyway (and fail).
8. Acquisition - Starts a new search with the dropped text.
9. Newsfire - Adds a new feed with the text as the address. (Why not try it out with http://feeds.feedburner.com/macosxtipsfeed )
10. Stickies - This will make a new Stickies note containing the text open up.
11. Dictionary - This will show you the definition of the dropped word. If you drop a selection of words, Dictionary will display the definition of the first. (In cocoa apps, it's probably quicker to use this keyboard shortcut).
Most of these also work if you drag the text to the desktop to create a text clipping first, and then drag it to the Dock icon.