I have found that constructing block elements oversize and then trimming them down to size works well for me. While a bit more time consuming, it allows for more accurate piecing. These are some of the tools I use regularly.
For trimming half square triangles, the 8″ Bias Square Ruler by Nancy J. Martin of Martingale.
Make your half square triangle slightly larger than the pattern calls for then use this ruler to trim it to the exact size required.
For making flying geese units, the Mini Fit to be Geese ruler by Open Gate Quilts.
Instructions include cutting measurements and clear directions with pictures on how to make flying geese units from 3/4″ x 1 1/2″ to 1 1/2″ x 3″. There is a larger ruler available for making units 1 1/3″ x 3″ to 3″ x 6″. Each contains a cool pattern.
For making square in a square units, the Square2 by Deb Tucker.
Instructions for cutting, sewing and trimming square in a square units from 1″ to 6″ finished size. The ruler can be used to fussy cut a design for the center square – very nice.