At Crate and Barrel, you'll find a non-stick, heavy gauge steel muffin pan that won't rust or warp.
At Pampered Chef, there's a reasonably priced ($16.00) muffin pan that bakes 24 muffins, tarts, or cupcakes.
The Williams-Sonoma Commercial Aluminized Steel 24-Well Mini Muffin Pan is dishwasher safe, extremely durable, and won't warp.
Another option at Williams-Sonoma is the Goldtouch™ Non-stick 24-well Mini Muffin Pan for $29.95.
Be sure to read the care and use instructions carefully to get the longest life out of your muffin pan.