When I was coming inside this morning from tending the animals, I noticed that the snow is mostly gone. There are still a few patches where we created snow banks when we shoveled the snow off the pathways or driveway, and being deeper and denser than the surrounding snow, they'll take a bit longer to melt. One of these spots is right next to the driveway on top of one of my raised beds.
When we first started gardening, we were complete novices (worse than novice, actually, and if you've read my book, I hope you enjoyed the story about my first adventure in gardening ;). Deus Ex Machina decided raised beds would be the best for the space we had available, but we didn't have any money for supplies.
We got our first rabbits at the same time, and we needed to have some place for them to live ... but, again, no money for building supplies or rabbit hutches.
Deus Ex Machina found some old pallets at work and brought them home. We used them to build a super structure for the rabbits (and more than ten years later, we still have and still use the hutch we made from pallets, although it's in need of a few repairs at this point) and with what was left, we built our first raised beds.
We've replaced and/or relocated most of those original beds, but it was a great lesson in making-do, and it helped us to realize that we didn't have to have the "ideal." Frankly, the plants don't really care, and with creativity and imagination, the garden made of repurposed materials doesn't have to look shoddy.
Since then, we've used all sorts of materials to create our beds. Right now, we have several 4'x 4' beds. These are framed using 1"x 6". We also have a couple of square beds that were framed using field stones from an old rock wall. Another bed was constructed of cinderblock (which are about $2 each and one needs fifteen to make one 8'x 4' bed).
My favorite raised bed material is the cinderblock, because I believe it has more longevity than wood (although the 1"x 6" allow me to make better use of my space, because I can place the beds closer together and still leave room for walking around the beds). Another nice thing about the cinderblock is that I can plant inside the perimeter of the cinderblocks, but I can also plant things in the holes of the cinderblocks, which increases my planting space without having to worry (as much) about whether the plants make great companions (because they don't share the soil).
Other perimeter materials can be just as simple and repurposed: buckets, plant pots, tires, bricks, cord wood. The possibilities are only limited by one's imagination.
In fact, I was looking out the window earlier, and I noticed that my neighbor had some old decorative shutters stacked under his storage shed, and I thought, "If I fastened those together, they'd make a good raised garden bed."