Some of my favorite MT sites.

http://www.mt911.com/ - Loads of information. Great provider search - you can search doctors by sound alike, location, etc.
http://www.drugs.com/ - Drug search is great! You can type in first few letters of a drug and get results, as well as any part of drug (say I hear a the last half of the word in which the dictator describes enter those letters and it will pull up results)
http://www.rxlist.com/script/main/hp.asp - This drug search I use to find dosages. I enter the drug into the search list and choose indications and dosages. I find this very helpful when unsure of the dosages given by a dictator.
http://adminsupportservices.com/mojoslinks/ - Lots of great links here.
http://www.transcriptiongear.com/ - Need a great pair of headphones? This site has a comprehensive list of transcription products. I usually find a product I like and look on Ebay for a cheaper deal.