Print on Demand (or POD) t-shirt sites are an easy way for people to get unique t-shirts that they might not be able to find elsewhere. They are also a great way for people to express their creativity by designing their own t-shirts. And they can even make some money by listing their creations for sale for other people to buy. These sites often offer other products such as mouse pads and mugs.
The most popular of all the print on demand t-shirt sites. Ease of use, quality printing process, a wide range of products, a good community for learning, and more make this a great place for people looking to buy or sell great t-shirt designs.
The forerunner of online print on demand t-shirt sites and probably the most well known. It's lost some popularity amongst t-shirt creators due to policy changes, but it's still a top contender.
This place focuses on quality. It also has a wide variety of choices to print your designs on. Most of these products require vector art though and only three colors, which is rather limiting. In exchange for that though you can get some interesting features such as glow in the dark and glitter, which other places don't have.
This site is newer to the scene of print on demand t-shirt sites. The site is lacking features that make it easy to use and pleasing to the eye compared to others. But quality printing and products help keep it in the top five. And as it grows it is expected to improve in the areas it's weak on.
The strength in this site lies in its community. It is a place for artists. While most popular t-shirts are funny slogans and the like, RedBubble is more geared towards artistic expression. This niche site amongst print on demand services might be what someone seeking to express themselves is looking for.
Whether looking at a print on demand t-shirt site just to shop for a more original shirt than you might get elsewhere or you want to try to make money by selling your designs...your best choice is probably Zazzle. But check the others out too.
ddrasoir, it is very hard for a top five list to be inclusive...I am aware of about a dozen more print on demand sites, but in a top five list I can only list my opinion on five of them.
Also, from your comments it is clear that what you were looking for was not a print on demand site but a fulfillment service...which it looks like you found. As I was not writing about fulfillment services I of course did not include sites such as Great Apparel For You...which I am aware of and do think sounds like a promising fulfillment service.
...But none of these listed services will brand my product. I really want a product that I can sell to the general public that looks like it's coming from my company--packaging & all. I only found one, Great Apparel For You. These other companies are probably great, but they don't necessarily serve everyone's needs. While the list is good, it's certainly not inclusive and those researching should Google Print-on-Demand Shirts, or Shirt Fulfillment Services, or things like that. Best wishes fellow entrepreneurs!