Take a look a
www.freeserifsoftware.com but make sure if you are using it for a commercial purpose you actually purchase the software. I believe if memory serves correct, if you just download the 'free' version you are not allowed to use the software for a commercial purpose, as part of the terms and conditions of the agreement. Nonetheless, the charged versions are approximately $10 or so and way easier to use than Adobe, in my humble opinion. Although I have purchased the full suite of adobe considering I do other work than just t-shirts. If you're look for 3D modeling etc.,
www.blender.org has a great open source software for this and just added a ton of functionality. Also search the forums here and you'll have great resources.
online designing software? 
