link  www.etymonline.com/ 

is a site that you can search words and it will tell you the origin of the word  

link  www.neilramsden.co.uk/spelling/searcher/ 

is a site that you can search a word part and it will give you all the words that have that word part.

link  www.neilramsden.co.uk/spelling/matrix/ 

is a site that you can put word sums in to the site and it will put it into a mini matrix.

link www.merriam-webster.com/wordfinder 

is an online dictionary.