News wrote that Eclipse 3.5 finally supports column selection. Unfortunately I don't know HOW to enable it. I tried pressing the ALT-key like I am used to in Visual Studio and all other Microsoft products but that had no effect.
How can I mark a vertical block in Eclipse?
Additionally, you can change the keys view window -> preferences then type: 'keys' and when the key preference page opens you can type 'toggle block selection' and voila!
On Windows and Linux, it's Alt-Shift-A, as RichieHindle pointed out. On OSX it's Option-Command-A (⌘⌥A). It's also worth noting that the two modes can have different font preferences, so if you've changed the default text font, it can be jarring to toggle block selection modes and see the font change.
Finally, the "search commands" (Ctrl-3 or Command-3) pop-up will find it for you if you type block. This is useful if you use the feature just frequently enough to forget the hotkey.