A few of my tutorials will leave you with leftover triangles of fabric. There are ways to make the quilt-along blocks so there are no leftover triangles but I prefer this way for accuracy and because I like to make mini blocks.
Take two triangles right sides together and sew 1/4" from the long edge (be careful not to stretch the fabric).
Press open and trim to 2.5" x 2.5"
Once you've finished sewing all four pairs of triangles, assemble into a pinwheel block (trim to 4.5" x 4.5"). Sash if desired.
There will be more chances to make mini pinwheels as we work through the quilt-along. There are lots of ways to incorporate mini blocks into your quilt (front or back) or they can be used in several other projects (doll quilt, wall hanging, pillows, etc). You can also arrange the half square triangles into other configurations or save them up to use in one big block. I'd love to see what you come up with. Feel free to put your bonus mini blocks in the flickr pool.