Here is a sample of the topics discussed:
item1 vs item2 = category1 vs category2 = example1 vs example2
Button vs Bottom = Object vs Direction, Location = icon vs down or below
Sentence example: click on the SEND button at the bottom of the page.

Programs
http://www.skysoftwarehouse.com/index.php?page=programs
http://wareseeker.com/free-english-pronunciation-software/ lots of programs
Type in a word below to find its rhymes, synonyms, definitions, and more:
http://www.rhymezone.com/
Quick Quiz: Verbs
http://www.rhymezone.com/r/dz.cgi?p=v
Randomly generated quizzes
http://www.rhymezone.com/r/dz.cgi?cmd=change
Pronunciation Power 1+2 CD-rom
http://www.esldepot.com/product.php/12/1/
Excellent Topic to explore:
Wikipedia:IPA
http://en.wikipedia.org/wiki/Help:IPAInternational Phonetic Alphabet
http://en.wikipedia.org/wiki/International_Phonetic_Alphabet
Wikipedia:IPA for English
http://en.wikipedia.org/wiki/Wikipedia:IPA_for_English