I picked up poweredge 750 from a friend today. It only has spots in it for two sata drives. I'm trying to find out if there is a cheap easy way to add more sata drives to for storage. I'm guessing external would be my only choice since there is no more space in the system. It does have two pci slots on the board. Is there any good options?
Yes, you need to add a controller/HBA (went through something similar with a PowerEdge 850 quite a while ago). The 750 has both a PCI and a PCI-X slot; which one you want depends on how much you want to spend and the performance you're looking for.
You need a half-length card (full-height is ok), which will limit your options a bit, and I assume something with with external SATA or eSATA connectors is preferrable, although you can probably do with internal connectors if you're willing to deal with threading the cables outside the case.
NB: I haven't checked the form factors on those units. In any case, LSI is what Dell OEM's for their controllers, so they tend to play nice, which is the primary reason I'd suggest them. If you want a Dell-qualified part, go to their site and use the Service Tag from your system to look for add-ons/upgrades/spares.