The delightfully useful Disk Utility built into OS X can burn disk images to optical media in a few easy steps. Read on for how to go about burning your new disc.
Windows users: You should check out the free ISO Recorder for similar functionality.
Launch Disk Utility (Applications > Utilities).
Insert your blank DVD or CD.
Drag and drop your .dmg or .iso file to the left pane in Disk Utility. Now both the blank disk and the .iso/.dmg should be listed.
Select the .iso/.dmg file you want to burn to disc, and click on the Burn button. A dialog box confirming the destination (your blank CD/DVD) will appear.
Sit back and wait while your new disc gets written!
All discs burned on the Mac work across platforms; you’ll notice in the screenshot that I’m burning the Ophcrack Live CD, which is obviously for use on Windows. This is a great way to back up software installation .dmg’s to optical disk to free up space on your Mac’s hard drive.