Ladies, do save those rotary cutter blades and then recycle them. Do not throw them in the trash as they do not belong in a landfill.
Here is a place you can send your blades on Exchange: No return postage is charged.
http://www.houseofhanson.com/lpsharp.html
He does not sharpen your blades for you, but will take your blades in exchange for a better price on blades. He does sell resharpened blades if you are interested.
Then here is a place that runs sales on the blades at a very reasonable price. I have bought these as well, but you will pay postage here.:
http://jhittlesewing.funoverload.com/sewing/specials/new_items.html
scroll way down to this point for the 45 mm blades. You will pass the 60mm blades on the way down.
Replacement
45mm Generic Rotary Cutter Blades
They work as well as any brand name blade.
One other note, if you are cutting grooves in your mat, then you are using your blades too long. You will be spending more money to replace the mat. I don't like dull blades, so find that spending the money to buy them in bulk makes sense. I have plenty of blades and will put in a new one rather than damage my mat.
CHECK IT OUT.