Now not only can you buy tees online, you can create, mashup, vote and share them. Here are some of the top tee sites online.

Threadless -  These guys combine shopping with a social network.  You can submit designs and slogans to be scored by the community.  Those that rank well, are added to the shop.  You can keep going back to this site and find new and exciting designs.

InnerTee - What do you get if you combine social networking, mashups and t-shirts? InnerTee of course.  To create a tee, simply mashup the available artwork and your left with a truly unique design.  Once finished, add it to the shop for others to buy.

T-Shirts Countdown - This is kind of like a top list site but for tees.  Anyone can add t-shirts to the site and users can vote for the best designs.  Could do a with a better design/layout and a better script.

T-Shirt Hell - Here you will find the funniest, rudest and crudest tees online. I got a laugh just by browsing through the shirt designs. Shirts are priced at around $18 and there is a huge selection.

Busted Tees - Not as crude as T-Shirt Hell but just as funny.  Some of the tees are priced as low as $9.99 which is awesome value.

Defunker - This seems to be the more serious side of Busted Tees.  Its run by the same people and offers the same quality.  These tees will set you back $20+

LMNO Tees - More funny tees in the feel of Busted Tees.  Not much more I can say

HotBins - Although you cant create the designs, you can vote on the ones you woud like to see printed.  Tees are $12 with free shipping.  Bargain.

SpreadShirt - If you’re looking to design (and sell) your own tees then you can’t go past Spreadshirt.  They use a flash based design tool which allows you to rapidly create t-shirts plus you can have your very own shop.  Think CafePress but with quality.

Zazzle - This site looks very similar to Cafepress.  Choose from a range of different tee designs and styles.

99dogs - Although it has a horrible design this looks to be the only site that offers custom tees as well as accepting PayPal.  So if you dont have credit card this may be your only option.