I've created a High resolution T-shirt mockup for Photoshop. Unlike other mockups you aren't limited to colors or size restrictions, you can display your art on a tee that actually looks printed and well done.
It's a high quality PSD file containing:
• American Apparel Tee layout.
• Multicolor shirt's available in all printing colors.
• Shadow & Highlight layers so your art actually looks printed.
• 300DPI at 7x5 Inches.
This file is available here: http://tinypay.me/~7c6eMUQ
Most, if not all other mockups range from $30~$500USD. This file is created with intentions of helping artists display their work at a more professional level, for a fraction of the price; or to help companies with proof issues regarding clients, helping them visualize a better finished product.
If you're a cheapskate and want to try before you buy, you can pay with a tweet too for a sample psd.