I'll be making a visit to the Library of Congress sometime in the next month. I visit the Library of Congress a few times each year to scan things which basically can't be found elsewhere. If there's anything in particular you want from the Library of Congress next time I go, let me know here. I'd strongly prefer that you've tried other resources first, and checked that what you want is in the Library of Congress catalog (or likely so; sometimes you can't tell).

I might also visit the NIST library and National Agricultural Library.

Also, if there's anything who is going to make a visit to the British Library or any major library in Russia (e.g., the Russian State Library, the National Library of Russia, Library of the Russian Academy of Sciences, any major academic library), let me know if you'd be willing to take some scan requests.