Silpats from the company Demarle are made of flexible fiberglass coated in silicone. This creates a flexible, nonstick surface that can be heated up to 480° and used over and over again. Spills and burned-on bits are easily wiped away. The silpat itself is also slightly tacky, so when you lay it down on your cookie sheet, it stays there.
We use our silpat in place of parchment paper or aluminum foil when baking just about everything. It's particularly great for baking very delicate things like crackers, meringue, and puff pastry. Because it's already nonstick, silpats don't need to be greased or otherwise prepped before use - a bonus for those of us who like to keep an eye on how much fat we use.
We also use our silpat quite a bit out of the oven. It makes a great surface for rolling out pastry dough or doing any kind of candy-making work.
There are a few drawbacks. You have to be careful what kinds of tools you use on the silpat since metal can snag the silicone and rip through to the fiberglass. This means that something like a pizza or a free-form tart needs to be transferred off the silpat before you can cut into it. Silpats also can't be used under the broiler or placed directly on the bottom of the oven.
Most silpats sell for around $25 and are readily available at any kitchen supply store. We found ours at Williams-Sonoma:
• Silpat Cookie Sheet Liner from Williams-Sonoma, $24.95
What have your experiences with silpats been like?