Markham, anyone?

I haven't found anything in Markham.

Endurosport is pretty good (in Toronto).

Not sure about Markham, but I use the following

Bike - Via Cicalante in Streetsville absolutely top rate service and knowledge. They will work with you to find the right bike/shoe combo

Running - Running Room on Wellington Street in Toronto again top staff and very helpful

Swim - Swim and Sports again Mississauga on Tomken Rd

Tri apparel a number of stores but my local is Du Tri and Run in Streetsville, prices are steep at times but staff are knowledgeable and actively involved in the sport

You may want to try Impala Bicycles in Richmond Hill (bikes only, but have some high end stuff) and The Running Room in Markham (running and tri stuff, one of the largest stores of its kind in the area).

Did you mean Running Room or Running Free?

Was thinking bikes when I posted before, but Running Free has some very nice stuff in their shop.

The main place in Markham would be Running Free on Denison.  They carry some clothes, bathing suits and wetsuits. 

There are two bike shops in the area,  Cyclepath on Main St. and Boyds in Stouffville.

As for swimming training in the area I've found that Centenial in the mornings to be pretty good.  Angus Glen just seem to be croweded.

Don't know of any clubs in the area.  Boyds tried to start a club a couple of years ago but they stopped the program. I think that they do rides and runs on the weekends, you would have to check though.  Running Room also does group runs.