DriveDroid allows you to boot your PC from ISO/IMG files stored on your phone. This is ideal for trying Linux distributions or always having a rescue-system on the go... without the need to burn different CDs or USB pendrives.
DriveDroid also includes a convenient download menu where you can download USB-images of a number of operating systems from your phone (like Mint Ubuntu Fedora OpenSUSE and Arch Linux). Around 35 different systems are available at this moment.
You can also create blank USB-images which allows you to have a blank USB-drive. From your PC you can store files onto the USB-drive but also use tools on your PC to write images to the drive.
Notes
• This application uses features of the kernel that may or may not
be available/stable on your phone. Tests have shown most phones
work without problems but please keep in mind yours might not (yet)
work out-of-the-box.
• Most kernels support emulating USB drives some support emulating
CD-rom drives and kernels with the right patches support both.
• Most Linux-related ISOs can be booted from USB drives but some
ISOs can only be booted from CD-rom drives or require some kind of
conversion.
Paid version
• No ads.
• Resizing of images.
• Add your own download repositories. Nice for companies or groups
that want to share custom or licensed images.
More info: http://softwarebakery.com/projects/drivedroid