These sites have proved useful to me in the past.

Adams and Stephens “Select Documents of English Constitutional History”

http://home.freeuk.net/don-aitken/ast/astintro.html

Numerous Chancery Documents

http://etext.lib.virginia.edu/etcbin/toccer-old?id=AnoChan&tag=public&images=images/modeng&data=/lv1/Archive/mideng-parsed∂=0

Various Documents from English sources,

http://www.british-history.ac.uk/period.aspx

Various items from Yales Avalon project, these the pre 18th C ones.

http://www.yale.edu/lawweb/avalon/pre18.htm

The Electronic Middle English Dictionary

http://quod.lib.umich.edu/m/med/

Las Siete Partidas of Alfonso X Il Sabio

-Spanish Law, The Seven Part Laws of King Alfonso X "The Wise",

http://faculty.washington.edu/petersen/alfonso/alfonsox.htm

Privy Purse Expenses of Elizabeth of York:

http://www.r3.org/bookcase/wardrobe/ward1.html

A collection of 15th C Grants of Arms, both Personal and Corporate.

http://verysleepy.itgo.com/grants.htm

Sven Norén's translations of Swedish Awards of Arms and a Knights Oath

http://www.geocities.com/sven_noren/Patents/index-eng.html

An excellent article, covering much the same ground as I am.

http://www.sca.org.au/scribe/articles/period_text.htm