I'm in the T-shirt and Promotional Products world (Or Branded materials). I only do large corporate and non-for-profit work, so I can't do them for everyone, but I can give some advice on the subject.
Lands End is a good place to get embroidery done on Polo shirts as well as jackets and fleece. If you want to stay local normally you can find a team or HS school spirit shop that can help you as well.
If you want t-shirts I recommend a local screen printer over Zazzle. Zazzle is good for 11 or under pieces, but if you can do 12 total I recommend going local.
Note: The more colors on a t-shirt the higher the price, especially on a low quantity (24 and below).
An embroidery set up charge can range from $40.00 to $120.00 depending on the stitch count. You can use the "embroidery tape" on hats, shirts, bags or anything you need. When you get an embroidery file set up, ask them when you get done to email you the DST logo file. That way you can use it with whomever and whenever you need it in the future. This will save you money down the road!
For Screen print, the set up charges will run between $10.00 to $20.00 per color/per location. You can do a digital print if the vendor offers but the colors are dull.
Other notes:
Cotton prices have gone up 10-20% over the last 12 months so expect to pay more for t-shirts than you have in the past.
Color t-shirts are more expensive than white shirts. I recommend a Gildan 100% 6.1 oz cotton shirt. It's your best bang for your buck. Don't let them talk you into just a T-shirt as there are some cheap and crap brands out there.
I know more info than needed :bored: but just trying to save you guys some money if I can. Donkey Punch BBQ might not get a lot of calls, but we are always well dressed!!!