I think you're going to find that it's usually the other way around. It's the companies / studios making the documentaries, radio ads etc. that will hit the web and search for companies / individuals selling sounds of whatever it is they need or rather record it for original use.
Some common big sfx stock sites like prosoundeffects.com might take your libraries on board if they fit into their product range but while stock music is a huge (saturated?) market with all major stock photo/video agencies having jumped onto that and some carrying sound effects, I personally found that it's usually not worth selling through those sites as an individual.
There are third party sites that aggregate some of these "indie" libraries together (one was mentioned in one of the recent tonebenders podcasts). If you want to sell your sounds your best bet is to create a site, list your sounds carefully in collections and make sure it can be found. Perhaps get together with fellow sound designers / recordists to create a more attractive offering and work together on libraries.
Personally I wouldn't bother cold calling / emailing any production houses unless you know for sure they need something that you can offer or your material is so unique that you are sure they will need it. Maybe you can elaborate a bit on what specifically you wish to license.
Looking forward to others chiming in on this subject as I think monetization of our work is always a hot and ever changing topic. And hey, nothing wrong with trying!