I currently use a 250gb Intel 510 SSD for my boot drive. I have a mix of WD and seagate drives. Before I started using SSDs, I had a WD raptor which is still in use right now. I have a total of 6 HDDs in my PC and the number is due to an accumulation of hard disks over the years and me not wanting to part with them.
The smallest capacity drives I have in the system is the WD raptor and the intel SSD at 250gb. The largest is a 1TB WD Black.