Listed below are interesting websites you may want to visit:

http://www.pbbook.com

1) This site offers you great philatelic literature. Need a book on your favorite subject?  Len Hartmann probably has it.

http://www.askphil.org

2) This site , managed by the Collectors Club of Chicago, can answer practically any question you have relating to Philately.

http://www.hawaiianstamps.com

3) This site is the most informative website ever created for collectors of Hawaiin stamps, Postal Stationary and Postal History.

http://www.psaginc.com

4) This is the expertising service I use on a regular basis and find to be very reliable.

Philatelic Stamp Authentication and Grading, Inc., (PSAG) offers authentication and grading of all United States, Canada & Provinces, Canal Zone & Hawaii. Their website has lots of interesting videos and other related information. You can also download submission forms directly from this site. Look for the red STARBURST and double click for forms."