Depending on the machine you're on... if you hold down the Option key as you boot you should be given the option to boot from any System folder connected to your machine. The downside is that it's pretty inefficient and it takes the machine a hundred years to search all your drives for a working System folder.
On my B&W G3 Holding down the option key at startup it will boot you into the first system folder on the primary hard disk. depending on how you installed OSX, if OS 9 is on the first partition (or hard drive); you can boot back into OS 9 by holding down option at start up. I have not tried this with 10.0.1 yet, but it worked in Build 4K78.
The boot option ONLY works provided you partition your drive. Have only one OS installed on each partition. When you boot hold down the option key and "OS picker" will function. It will take some time if you have many drives/systems installed. Really long with a System CD inserted too. Although you can have OS X on one and OS 9 on both you will notice that 10 will only "Bless" the OS 9 sitting on the other parition. Hope this clears this issue up.