I've ordered my last 3 systems worth of parts from
www.ncix.com in Vancouver. Great prices.
Are you gaming with the system?
IMO, one of the best boards out there now is the Gigabyte DS3L. Pair that up with 2GB of OCZ ram and a Q6600. Or wait for next week if you're willing to spend a bit more, the new Q9450 is supposed to be out this coming week. It's the new 45nm core, 2.66GHz, 4 cores and 12mb of cache.
If you're gaming, either the G92 based 512MB 8800GTS or the new 9600GT. Nvidia is supposed to be releasing their new 9800GX2 this coming week as well.
If you're not gaming, something like an 8600GT will be fine.
For HDD, I'd go with either Western digital or Seagate. I love the seagate drives, but if you ever have warranty issues, you have to ship the drive to the US while WD has a repair centre in Canada.