I checked out a few tutorials online, and the following are my favourites for different types of hems:
I love doing hems by hand. There's something nice about taking a little handsewing break, especially if you've been fighting with your machine (a frequent occurrence in my life).
The first two links show a similar stitch (I usually use the first method), and the third is a bit of a quickie. Make sure you take an extra stitch (or knot your thread) now and then, so that if part of your hem breaks, you don't have to repair the whole thing.
SewForDough: Hand Sew a Hem
The Sewing Divas: Hemming Stitch by Hand
Craftzine: Quicker Hand Blind Stitch
A blind hem can also be accomplished on a machine, but it's not nearly as good. It's more appropriate for pants or thicker fabrics. When you do a blind stitch by hand, you can really pick up only one thread, rendering your hem truly invisible. On a machine, a lot more is picked up and you end up with a small vertical stitch every inch or so. Still, if you're doing a huge panel of drapery or something, go with the machine stitch!
Threadbanger: Blind Hem by Machine
Normally when I hem jeans, I just fold over the edge twice and sew it with a nice heavy jeans thread. But I do mourn the loss of that special, unreproducible look of an original jean hem. Here's an interesting way to preserve the original hem. (Oh, apparently it is known as a "Euro Hem". How fancy.)
Sidenote: I love my Jean a ma jig. It's so simple yet brilliant. Keeps your machine from getting angry and skipping stitches when you go over the bulky seams in jeans.
Dacia Ray: Jeans Hem
A narrow hem is lovely in a fine fabric. Both of these techniques use guide stitches to help you fold such a small edge accurately. The second technique adds an extra step of stitching and trimming to achieve a super narrow hem, and is perfect for slippery, hard to control fabrics.
Chickpea: Narrow Hem
Marcy Tilton: Calvin Klein Hem
Rolled hems are even smaller and finer. They can be done by hand or by machine. I must admit, I have never had fun doing a rolled hem by machine. They're much easier with a stable fabric. Chiffon will make you crazy, and I would definitely pick a hand-rolled hem if faced with that prospect.
The Sewing Divas: Machine Rolled Hem
Colette Patterns: Hand Rolled Hem
If you have to hem a corner, a mitered finish is a really nice touch. It reduces bulk and just looks so tidy and professional
Burda Style: Mitered Hem (simple)
Craft Stylish: Mitered Hem (in depth)
Special cases require special measures! Sew For Dough has some great tutorials for doing tapered or flared pants, as well as hemming stretchy fabrics.
If you have any other links to share, please post them in the comments.