Printing.

I love the art of printmaking in all its forms--letterpress, woodcuts and linoleum cuts, lithography, etching, screen printing.  Hell, I love what can be done with a rubber stamp or half a potato.  (Some pretty sweet potato art can be found here.)

Printmaking really fits my ideal of the perfect craft, because it fulfills every requirement on my 'Learning New Things Checklist'

Anna's Learning New Things Checklist:

1. It must not be cost-prohibitive.  Basic tools must be available in a brick and mortar store somewhere I'm willing to drive to, and reference material must be available online or in my local library.  If I progress and want to invest in supplies and reference materials beyond what I can find in my city, I am willing to do mail order or online ordering to get supplies.  But if I'm just scratching a crafty itch, I need to be able to find extra materials before I lose my craft momentum (craftmentum).  The amount of money I'm willing to spend on learning a craft is different for each craft.  It depends on how rich I'm feeling, how much the materials cost, and how likely I think it is that I'll succeed.  But generally, if I can't get started with the bare bones basics for less than $50, it takes me longer to decide to dive in.

2. Low fuck-up factor.  Nobody likes fucking up.  I'm actually okay with it, as long as I'm not ruining something I have a lot of time/money/effort invested in.  When I'm thinking about Learning Something New, I need to feel like I can learn and make mistakes and get my hands dirty without ruining all my materials or ruining materials that cost a lot of $$$.  The best crafts produce great results at every step of the learning process, and over time yield a product that shows the skills you've acquired.

 That's my whole list right there.  And guess what?  Printmaking fulfills both of those requirements.

My personal experiences with printing is in the potato/woodcut/screen printing area, heavy on the potato.
I've done a lot of carving, and a fair amount of screen printing, using the embroidery hoop method (or cheating method).  I love the embroidery hoop method of screening because it's inexpensive, easy and effectively teaches the method of blocking the screen and passing the ink through it without jumping straight into photo-emulsions, which still terrifies me slightly.  I still screen on embroidery hoops, mostly because I keep finding huge ones at Goodwill for like a quarter.  I have invested in some real squeegees, instead of using cardboard, because they are gentler on the screens.  (If you take care of them you can use them practically forever.)
Linocuts are great, because you can get the linoleum blocks inexpensively at most craft stores, and because even amateur carvings can look very stylistic.

This is a picture of my brain iron-on patches, which are printed using a linocut.  (It's very similar to using a potato, except instead of a potato, you use a block of linoleum.  The benefit of using linoleum is that it stores better over time than a potato, so you can use it many times.)  The  brain is the first linocut I ever did. 

Here are some cassette tape patches.  Same linocut process, you could easily substitute a potato, or a yam.  I've never printed with turnips or radishes, but I'm sure that would work, too.  Also a carrot would make a cool sealing wax monogram if you were willing to re-carve it every time you did some letter writing...

Here's a cool resource on beginning linocuts.

 ...and because I have had so much fun going through my printmaking folder, above is a piece I sold in 2008, titled 'this anatomical life.'  You can't see, but there's lettering on each one, heart, mind and soul.

And below is a little gnome.  He's about 4" high.

Not to shamelessly plug, but all my printed patches are in my etsy store here.