Personally, I don't care for the look of cinderblock. I have used treated wood which works fine and will hold up for a number of years. Now that they don't use Arsenic it should be safer, although I never saw conclusive evidence it was all that bad before. Using some of the new manufactured wood that is made for decks might be an interesting and slightly expensive option. There are as many different kinds of concrete edging blocks as you can think of that can be stacked. Kind of expensive too, but unless you are building a lot of beds are probably budgetarily manageable. In the old days, tires were even a popular option. It is all in the imagination. Have fun and who cares what the neighbors think as long as you like it. :-)

I'm using railroad ties and like the look a lot.

Kittee,
I've used cinder blocks. For a picture go to the
link I've posted. I've been planting in this
raised bed for about 5-6 years now. It's gets
nicer every year. Good luck.

Brenda

Here is a link that might be useful: Community Webshots

I have some big chimnny pipes (square clay) with stuff planted in them, plus some big pots. One day we'll have raised beds in the front too. When I was in Texas I saw a lot of raised beds made out of old metal horse troughs; they looked great but I find they are hard to obtain. Big old washtubs are good and so are old washing machine drums!
You could (I've done it) have a big container filled with compost and have pots on the top (you can move a pot, put food scraps under it, cover with leaves and then the pot...)
Be sure you hide it well so you don't get animals disturbing it. My favorite (although I have not done it) idea I ever heard for making raised beds was newspaper sides. Yes, newspaper. The guy would soak the paper until it was very wet, then lay it (folded over) in lines and layers to build up walls. The layers dried into solid walls that slowly biodegraded; he would replace parts of the wall periodically. The newspaper developed a patina that looked natural; a kind of grey brown surface. A bonus was that it absorbed water and released it nicely so he did'nt have to water as much (important in the summer when you may end up watering twice a day just so half your stuff will survive.)
No, I can't find the link anymore and I tried, really.