Snow Leopard should allow for on-the-fly partitioning and partition resizing. AFAIK, this is not just limited to the BootCamp Utility. But I don't have my main drive partitioned, so I have not used it.
As far as partitioning and then doing a fresh install of Snow Leopard. I would recommend that regardless of whether you plan to partition, BootCamp or whatever. I do that with any new Mac I get. The reason: the default install of OS X is somewhat bloated. You can cut out upwards of 6GB by removing the ability to change the OS language to one of 10 to 15 languages. You can also remove other components like additional language support for typing (with you OS still in English) in other languages. If you don't have a use for it, take it out. OS X also comes with support for almost every printer out there, making printers plug and play. You can either leave those, or just download and install the driver for your actual printer(s), which will give you the latest driver anyway. There is also X11, which you may or may not have a use for. It's almost always a good idea to wipe and do a clean install of the OS, tailoring it to your uses and needs.