US citizen/Can resident - VISA requirements

Yes, you can apply in Toronto is you reside there. The invitation letter should include following information:
1. Your personal information: name, gender, date of birth, passport number, etc.

2. Information concerning your visit: purpose of the visit, date of arrival and departure, places to visit, relationship between you and the inviter, and who will bear the cost of your accommodations.

3. Information of the inviter: name of the unit or individual, phone number, address, and the legal representative or the inviter's seal, or signature.

Generally, a fax, copy or printout of invitation letter is acceptable.

Thank you for reply - that was very helpful.

Also, since I am traveling because of work, and I'm applying in a country or territory (Canada) other than the country of my current nationality (USA), should I also complete the Supplementary Application Form besides the V2011A Application Form?

Yes, you should fill the supplementary application form V2011B.