The last time I did any "free samples", it was for some 8-bit ADC chips from National Semiconductor; back then I had to call them up (pre-public internet days); they sent me out a tube of 5 that I never used (I was going to make an audio digitizer for my Amiga 2000, and never got around to it - that's how long ago it was!).
It used to be on some vendors sites (maxim and microchip, especially) you could easily request a sample online, without too much hassle. Since then, things got abused by dorks who used it as a supply point (maybe even reselling them on ebay) without actually purchasing a quantity afterward. Things have been tightened down, since then.
I think its still possible, but you might want to call the places up instead (go old-skool), talk to a real human, explain your need - they may take pity on you. Another route might be to look into chinese suppliers for certain parts and/or components. A friend of mine who was working on my robot project with me a couple of years back scored us a donation of a 200 or so mW green laser pointer from some chinese supplier (this was pre-ban days) we planned to use for a LIDAR system (it still may get used!). You might try that route (I'm still not sure how he pulled it off).
