The Geeky Hostess as part of her excellent series on etiquette. You can read the post here.
I'd like to add that when curating this year's list I purposely included a few items that a geekling (grown up or otherwise) could give to a mom who isn't necessarily a geek. I think it's important when giving gifts to honor the recipient by giving a gift that also has a bit of the givers personality. So you could give a gift like the molecular gastronomy kits as a science/culinary fan to a mom who may not be a geek but would appreciate doing that sort of project with you.
Anyway, head over to The Geeky Hostess and check it out!