Nagging is just another form of reminding, isn’t it? How you feel about the subject dictates whether you think of a reminder as a nag or as a helpful productivity tool.
There are lots of ways to nag yourself; put books by the door that you have to kick out of the way if you’re not going to pick them up (and return them to the library), stick Post-Its on the mirror where they block your view, leave things out where they’ll visually bug you till you do something about them.
And now there’s HassleMe. This service lets you compose your own nagging emails and then sends them to you on an irregular schedule. Since you won’t be expecting them, you can’t tune them out quite as well as your own homegrown nags.
I could also see using this service for non-nagging purposes, such as sending myself encouraging notes. Or to remind myself of things I actually want to do, but tend to forget about.
Thanks to this Mashable post for enlightening me about HassleMe and 99 other nifty productivity tools.