yes you can. and it is easy, really.
if your pc has a firewire interface installed (it doesn't matter if it's the 6-pin or the 4-pin connector, there are converter cables available), then just buy any firewire hard drive that has an oxford911 chipset (lacie d2 for example). first format it in pc as a fat drive (not ntfs), transfer files to the drive, and disconnect it from the pc. go to your mac, connect the drive, transfer your files, and be done with it.
but if your pc only has usb, you have a choice:
1) buy a cheap firewire-card to the pc you are abandoning or
2) buy a firewire/usb combo drive instead.
i would do the former, but many would choose the latter. cost should not matter, because combo drives are likely as much more expensive compared to firewire-only drives as the cost of firewire-card would be; and i know many would want to leave the drive formatted as fat to keep the pc-compatiblity. i would however recommend formatting it as hfs, because that's what mac os x wants to use.
so... after you have your files safe, re-format the drive in mac os using disk utility and selecting the hfs file system instead of the existing fat. remember - after formatting drive to hfs the drive will not work with pc:s anymore, but has advantages in your new mac environment.
not so bad?