Here are some links that I thought were very usefull,

customizers that know what they are doing, but also give you good ideas and
provide a nice set of links and tutorials on their page, check them out!

http://www.tonyzcustomz.com

http://www.jinsaotomesdangeroustoys.com/


Transformers sites that contain all the information you might want or need.

http://www.tfw2005.com/

http://www.seibertron.com/

http://tf08.net/

http://www.allspark.com/

Supplies for the average customizer

http://www.hobbyfanatics.com/

http://www.gaussboys.com/

http://www.hlj.com/

http://www.miniatronics.com/