1. Brighten Her World- Nothing says "I love you, mom" like showing up early Sunday morning with some window cleaner and washing Mom's windows, inside and out. Bonus points for not creating clutter and being nearly free. Yes, it requires you to live near your mom, but frankly, if you don't, and you didn't send anything, you're in a delivery or Amazon gift card kind of bind.
2. Grow Some Love. Plant her garden for her. This is particularly great if your mom loves a garden but has trouble getting down on her knees for the intensive start of season planting. This is what I do, every year, for my now 80 year old Mother-in-Law. Picking up a tray of flowers is not expensive (less than $2 for 6 plants, at most garden centers I've visited) and can put a lot of color in her yard.
3. Bind a Memory. Check out the myriad book binding tutorials online. They're fabulous, easy, and can be done with stuff you probably have on hand. If your mom is anything like my mom, she'd love a small handbound book (yay printer paper) to toss in her purse or keep by her bed for jotting down all those fleeting thoughts you and I would just tweet to the world and then not be able to find later. Bonus if you've got some lovely scrapbook paper laying around for a cover.
4. Girl Time. Forget the expensive spa, just you and mom having some good old fashioned girl time, at home. Do each other's nails, make a scary face mask out of stuff from your kitchen- just have someone else watch any of the littles who might detract from the calm of your time together.
5. If you don't have time for any of that, hit up the office supply section of your local box store, because I have yet to meet the woman who can't use a nice pencil sharpener or a good pen, and it's all under ten bucks.
If you're wondering, I just want my husband to fix my leaky faucet, and for my mom, I used the scrap wood in her garage to build the raised beds she's been asking for. Yay free!
Good luck, and Happy Mother's Day.