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.
I went to the Library of Congress today. It's highly likely I'll go again next summer, so you can still let me know if there's anything you want scanned.
Over the last year, VincentYu, gwern and others have provided many papers for the LessWrong community (87% success rate in 2012) through previous help desk threads. We originally intended to provide editing, research and general troubleshooting help, but article downloads are by far the most requested service.
If you're doing a LessWrong relevant project we want to help you. If you need help accessing a journal article or academic book chapter, we can get it for you. If you need some research or writing help, we can help there too.
Turnaround times for articles published in the last 20 years or so is usually less than a day. Older articles often take a couple days.
Please make new article requests in the comment section of this thread.
If you would like to help out with finding papers, please monitor this thread for requests. If you want to monitor via RSS like I do, many RSS readers will give you the comment feed if you give it the URL for this thread (or use this link directly).
If you have some special skills you want to volunteer, mention them in the comment section.