To show a listing of available OS's at startup, hold down the option key (may be alt in other countries). However, I have found that this does not show my OS 9 installation, just OS X. You should be able to manually eject the CD by looking for a small hole by the drive and inserting something small and pointy, like an unbent paperclip.
2.5 GHz MacBook Pro Core 2 Duo, 4 GB RAM, 320 GB hard drive, runs 10.6.8
1.6 GHz iMac G5, 1.5 GB RAM, 120 GB hard drive, runs 10.4.11 (out of commission)
iPhone 4, 16 GB, iOS 4.3.5