These are the "official" sources of load data that are available on-line, that I have been able to find. If you know of more, please include them in your post. I will add them to this list so as to serve as a convenient, single-source reference.
Please send me a PM if you know of additional, authorized sources or if a link is incorrect/outdated.
Accurate's Lt-32 data
ADI Powder Guide
Alexander Arms 50 Beowulf Data
Alexander Arms 6.5 Grendel Data
Please note: Considerable data from Alliant can only be found by going to the "Products" link, selecting the powder in which you are interested and selecting the "View All XYZ Recipes". A great many loads do not show up in the Data Library directly.
2010 Alliant Reloader's Guide
2013 Alliant Reloader's Guide
2014 Alliant Reloader's Guide (pdf format)
2015 Alliant Reloader's Guide (pdf format)
Hodgdon, IMR and Winchester
Hodgdon Basic Manual, 2008
IMR Handloading Guide, 2003
IMR Handgun Guide
IMR Trail Boss Reduced Rifle and HANDGUN, lead AND JACKETED Loads
(As of mid-2013 contains ALL Nosler data)
Sierra .300BLK Data
2015 Vihtavuori Reloading Guide (pdf)
CAUTION: The following sources include either all unofficial or at best mixed loading data from official, unconfirmed and unofficial sources. USE AT YOUR OWN RISK. Neither the writer, The Firing Line, nor the staff of TFL assume any liability for any damage or injury resulting from use of this information.