It's a word processor combined with a calculator, a decimal converter, a dictionary, an image viewer (with full screen mode), a movie player, a font browser, and sticky notes. There's little here that's not already available with apps that come with your Mac, but if you find them lacking in some way, DigiTools may be worth a look.
Smultron has recently reached version one, and has been getting a lot of good reviews. It's open source, so there should be no worries about the author updating and charging for it.
SubEthaEdit is an ingenious program that lets more than one person edit a document at the same time. Even if you don't need this function, it's still a great program. The latest version is free only for non-commercial use, which seems fair.
Back when the Web was young, I learned HTML with a shareware program called PageSpinner, which I would still recommend for learners. It's not free, though, so the next best thing would be Taco HTML Edit. It's a bit lacking in professional polish, but a lot of people swear by it.
Bare Bones has updated TextWrangler and is making it free. It's got a lot more features than BBEdit Lite, so why not go for it. But watch out -- you may find yourself wanting to upgrade to the wonderful BBEdit.
uEdit was recently updated to version two, and looks to have a lot of good features. I was quickly able to do some basic HTML without much need for instructions. Definitely worth a try.
Font management is taken to a whole new level with this widely praised program. If you're not happy with the built-in solution provided by Apple, give this one a try.
Pump up the free TextEdit that comes with your Mac by adding this well-done thesaurus from Nisus. Just select a word, and look it up with your Services submenu.
Type in a couple of letters, hit the space bar, and the text expands to whatever you want -- including pictures. It's not only easy to use, but easy to set up.
It reorganizes text into narrow columns and let's you side-scroll through it -- making it easier to read. I was skeptical, but once I tried it, I was impressed with how well it works.
Add a number of services to your free TextEdit, along with Nisus Thesaurus, and you've pretty much got a free, full-featured text editor. Find a bunch of other freeware you might like at the above URL.