I found two very useful tools that I wanted to share. Both are photo manipulation tools , along the lines of Photoshop, but have the advantage over Photoshop, in that they are free!
My new-old iMac came with iPhoto, the standard package that Macintosh gives you when you purchase a computer. Like all comes-with software, it is barely adequate: I can crop a photo, or lighten/darken it, and that's about all. So I went in search of some better options.
The first thing I found was GIMP, a free photo manipulation software to download. I wish I could personally vouch for GIMP, but I was not able to download it, because my version of Mac's operating system is too old. I've got 10.3.9, and I need 10.a million. Or something. But it sounds really cool, and it would be convenient to have to software. Convenient but not crucial, because the next thing I found was Picnik! Picnik is a website that allows you to upload photos, do your manipulation online, and then download them or export them to sites like Facebook and Flickr.
I was able to create the strip collages at the top of this post using the free version. I like it so much that I, the world's cheapest human, am considering upgrading to the pro version, which costs $25 a year. The downside of Picnik is that it loads and responds quite slowly, but that may be just my elderly computer, the one which was deemed too stupid to handle GIMP.