In the age of computers and smartphones, penmanship is becoming a thing of the past. Adults can barely scratch out cursive; how do we expect children to fare any better when they've grown up wielding technology? Still, the need to be able to write isn't obsolete, and we neglect that element of our children's education at our (and their) own risk.
We really do recommend using a good penmanship course, like Getty and Dubay's Italic Handwriting or A Reason for Handwriting. Yet regular practice is a good idea, and some of these worktexts can keep methods and forms in kids' minds. Be careful, though! You don't want to end up giving your kids books following a different format than what they learned initially; that'll simply confuse and frustrate them.
If they demonstrate a natural talent for (or particular interest in) penmanship, you might consider having your kids learn calligraphy. It's a particularly demanding form of writing usually reserved for art or special occasions, but it can support the development of fine motor skills and even drawing ability like mere cursive and manuscript writing can't.
A popular program at Exodus Books is Startwrite, a Mac/PC compatible CD-ROM that lets you create your own handwriting sheets for your kids. Whatever resources you choose to use, we strongly encourage you to make sure your kids can write clearly and efficiently. Who knows? If the iPocalypse actually strikes, we may be using exclusively paper and ink again for a very long time.