These non-toxic silicone coasters look good on their own, but can be personalized time and again using a ballpoint pen, 4 for $21.
DIY Twig Coasters
Directions from Martha Stewart
6, 6x6 samples for $6. Image via Moment of Inertia, Flickr
These come packaged in a metal tin with circuit board top, 6 for $25.
Make your own, or buy at 3RLiving, 6 for $18.
Vinyl Record Coasters
By stellajames, 4 for $24.
DIY Woven Cork Coaster
Directions from Ready Made
By FilzFelt, 4 for $12.
1, 4x4 sample for $4.
Made of traffic signs, by Boris Bally, 4 for $85.