Given the choice, would you rather be wearing the same logo as everyone else around you? Prominent company logos have always made me laugh a little - you pay extra to advertise for the very people whose profits you are adding to.
So what choice do you have? Well you could either wear plain, unbranded tops, or, you could design your own instead! If you are reading this post, you already have all the equipment you need to design a Custom T-Shirt; a computer and a connection to the internet.

I have dealt with VistaPrint before, when helping John out wish some electronic business cards, so I feel sure their Custom T-Shirts Printing process is of top notch quality.
If you prefer, you can select from their range of template designs, and add some text if desired, though I find the option of uploading your own artwork more appealing personally.

If you are seriously into your digital artwork already, you will find the company accepts all the common standards, ranging PSDs, PDFs to Illustrator’s AI files. However, if you have just seen a high resolution picture that you would like on your very own t-shirts, then you can always just upload a JPEG or GIF.

The original links I found for the site are listed above, but if you would prefer to go directly to the T-Shirt section, please click here.