macfidelity

Apple docs for that topic here

In short:

Resetting PRAM and NVRAM

1. Shut down the computer.
2. Locate the following keys on the keyboard: Command, Option, P, and R. You will need to hold these keys down simultaneously in step 4.
3. Turn on the computer.
4. Press and hold the Command-Option-P-R keys. You must press this key combination before the gray screen appears.
5. Hold the keys down until the computer restarts and you hear the startup sound for the second time.
6. Release the keys.

OsXDaily posted 11 Startup keys for Intel Macs

Howto boot from CD or DVD:
Press C during startup
Start up from a bootable CD or DVD, such as the Mac OS X Install disc that came with the computer.

Howto run Apple Hardware Test:
Press D during startup
Start up in Apple Hardware Test (AHT), if the Install DVD 1 is in the computer.

Howto Reset NVRAM:
Press Option-Command-P-R until you hear two beeps.
Reset NVRAM

Howto access Startup Manager:
Press Option during startup
Starts into Startup Manager, where you can select a Mac OS X volume to start from. Note: Press N to make the the first bootable Network volume appear as well.

Howto eject devices:
Press Eject, F12, or hold the mouse (/trackpad) button Ejects any removable media, such as an optical disc.

Howto Netboot:
Press N during startup Attempt to start up from a compatible network server (NetBoot).

Howto startup in FireWire Target Mode:
Press T during startup
Start up in FireWire Target Disk mode.

Howto boot in safe mode:
Press Shift during startup
Start up in Safe Boot mode and temporarily disable login items.

Howto verbose boot
Press Command-V during startup
Start up in Verbose mode.

Howto boot Single-User mode:
Press Command-S during startup
Start up in Single-User mode.

Howto netboot:
Press Option-N during startup Start from a NetBoot server using the default boot image.

Thx for that summary.

Source: OSXDaily.com