I'm a big fan of cinder blocks, myself...but they take up a rather big footprint because of how thick most are.

That said, they're sturdy and very long lasting. Some people plant stuff in the holes of the larger ones (flowers, carrots, radishes, salad greens, etc).

My next permanent raised beds are going to be exterior painted and tiled (purely decorative) cinder block. I know people with 20+ year old raised beds made out of cinder blocks that have needed very minimal patching up over the years.

Oh yeah...it seems that materials are important to you, so if you do go for cinder blocks you might want to make sure they're not made from concrete containing flyash/coal ash. Some places may have no idea, though.

I have used plain wood dimensional lumber for years and years, and this is termite territory. No oils, no paints, no sprays designed to kill something. It's dry here.

They seem to last forever, perhaps because even though one side may be wet the outside is dry? I dunno. Some beds are made from stacked 2X4 scrap, others from wider lumber, and they all seem to grow higher every year or two. Starting out at twelve inches can be a lot of extra work, and as a wild example a three foot by ten foot by eleven inch bed will eat a cubic yard of material in one bite. Starting "thinner" might not be any problem.

When grubbing close to the ground I think materials matter little other than in what to avoid. Block is good. Plain wood is good. Heck, manhole covers lined up like Viking shields would work. Vinyl has problems, perhaps specious, but I think it's something to avoid.

If you see a pic of nc-crn's setup, be sure to bow just a little.

The plastic the fencing is made of will not leach anything "nasty" into the soil, although I'm not all that sure the fence material will do what you want it to. I have used untreated 2 x 6 SPF as sides for planting beds and have had them stay in good condition for several years. Some are beginning to show signs of deterioration 25 years after being laid down.
I have also used various types of cement blocks, pavers, the 8 x 16 builders, etc. and have found the holes in the builders tend to fill up and grow unwanted plants.

Thanks for the responses. I like the idea of block and may try that, however I forgot to mention I am also charged with planning and creating a community garden at my church. The garden will be in a fairly prominent area, so I would also like the beds to look uniform. Space would not be an issue at church, but will be in my yard.

Nc-crn- I like the idea of block, but I am concerned about blocks shifting and sinking. I don't want to cement them in.

Kimmsr-what is SPF? I think if I use block, I would either buy caps or fill with soil and plant the holes.

Grubby - I am concerned about rot, the reason I want to do it in my garden is it is not well drained. I have been discouraged by several locals from doing it, but I'm not so sure. Many of them said, "just use pressure treated lumber", and "I'm organic" in the same sentence!

I'm not in your neck of the woods but here there's very little rot. Maybe you're over-worrying rot and decay, and maybe frugal water management ways like drip irrigation could cut rot way back for you. Also realize that garden dirt isn't moving and dynamic. It just sits there like a lump of, er, uh, dirt(?). Blocks don't sink. Boards don't bow. Water doesn't run off unless you have way too much. Coyotes don't dig it up unless they're after your gophers. Maybe if you check out square foot gardening to see how those guys treat beds just like large pots and realize there's little to worry about.

Church, eh? There's nothing that says this stuff has to look sloppy or crude.

If you wanted to go with 2 x boards you could, if the stuff is ok for organic, make up a saturated copper sulfate solution and paint it onto the boards prior to building the bed. The boards will resist rot much longer with the copper sulfate treatment. I don't know if this passes as organic but then, killing perfectly good trees to build a bed doesn't make much sense either. I'll leave it to others to debate the ethics of using other materials like block and plastics.

SPF in the lumber world means Spruce, Pine, Fir. That means the 2 x s you by could be from any one of those trees.
I saw a study some years ago that indicated treating wood for rot resistance might add one or two years to the life span of that wood. My experience seems to support this.

I've had good luck using the commercial copper preservative on the inside and bottom of the board, letting it set. and following that up with a couple coats of boiled linseed oil. I am in a hot, dry summer area though, so the early beds had problems with the outside of the boards cupping away from the soil. Once I went to more heavy-duty fastening methods, that issue seems to have resolved.