I quick way to classifiy them is to count the pins!
There is a definite physical difference from a DDR and a SDRAM. DDR has 184 pins and SDRAM 168 Pins: DDR2 has 240 pins. There were the older type RAM which were 30 and 72 pins.
As to find out there frequency (PC2100>PC3200) etc., you'd have to test them on a motherboard to find out.
Asus P4P800 SE
Intel P4 3.2 Gig 1024 Meg PC3200 cas latency 2.5
RAID 0 2-36.7 Gig SATA WD 10,000 RPM
200 Gig WD ATI ALL-IN-WONDER 9600XT
6500 Kb bandwith Internet Connection