Op Amps from Texas Instruments

www.ti.com

TI is currently one of the biggest IC manufacturers.
And the fastest in providing free samples at that. Samples are shipped out immediately via Fed-Ex without you being pestered by phone calls.

I have listed below few of TI op amps that I recommend . Try requesting samples for evaluation. All of these are available in DIP package.

OPA137P
OPA2336PA
OPA4137PA
TLC252CP
TLC272CP

Based on my experience, TI is very reliable in providing samples quickly.
But do not abuse this sample service as you might get banned!