http://www.io.com/~hcexres/tcm1603/acchtml/twspell.html
Online Technical Writing: Spelling Problems
This webpage covers the most common conventions--or rules--concerning grammar, usage, and punctuation. If you have problems with spelling, they may only be a few specific areas that you can overcome once you identify them and practice a bit. The page reviews some of the most common areas of spelling problems.

http://homepages.cambrianc.on.ca/tutorial/thetutorialcentre/writing/spelling%20improvement.html
Spell Right!
Could your spelling use some improvement? Try the quick quiz on this website and find out.

http://www.netfunny.com/rhf/jokes/87/2094.10.html
Mark Twain's plan for the improvement of spelling
A humorous look at how spelling in the English language might be improved.