BEANG  hardcore users / developers NEED this. can't live without it.  
(Version 0.13)

CHRONICFATHEAD  This is an excellent boot manager. I used to miss pressing the alt key when my MBP started up, and would have to reboot again. Now I have rEFIt I don't have any problems.

It's big, clear and reasonably stable. I say reasonably, as every now and again when I boot up I don't get the choice. I haven't worked out what I've done before it happens, as it happens so infrequently.

Well worth the download!

So good, when I've had to set up dual booting for customers Mac's, I always install it.  
(Version 0.13)

MICHAEL KWASNICKI  This ist not a normal boot manager. With this tool you can also boot Linux or other OSes from external harddrives which is not supported by BootCamp. This enables the ability to not only use the internal Harddrive where you have to create partitions that limit your internal disk space. You can use dedicated external harddrives for the OSes. And that is awesome.

(just bad that Windows does not allow to be installed on an external Harddrive even it recognizes it)  
(Version 0.12)

ISTUNTMAN  Very nice and easy to use boot manager. Must have if using Boot Camp. This app makes rebooting pleasant.  
(Version 0.10)