After a few months of experimenting with photography primarily using a plastic-lensed Holga 120, I was ready for something a bit more serious. I wanted an entry-level 35mm SLR that gave me the ability to focus precisely and have control over exposure without being fully manual. It goes without saying that there are many cameras from a variety of brands that would have met my needs; because the options are plentiful to the point of being exhausting, I settled on the first I could find for cheap and ended up with the Canon AE-1. The Canon AE-1 was a highly successful offering from Canon and are easy to find on the used market.
Some choose to learn the basics by shooting fully manually with their first film camera, and I respect that. However, for casual shooters I think that having a bit of a crutch doesn’t hurt. The AE-1 can shoot in metered manual mode, in which a needle in the viewfinder indicates what your aperture should be based on your shutter speed choice. Thus, it’s still possible to learn the relationship between settings in the exposure triangle (ISO, shutter speed, & aperture). As a tool for amateurs, it works well in shutter-priority automatic mode; you choose a shutter speed and the camera decides upon the best aperture for you based on the lighting conditions. The similar AV-1 is an aperture priority camera with near identical build. There's also an A-1 that is fully exposure-automated, choosing both aperture and shutter speed for the user.
I’ve owned a few AE-1's over the years and don’t have any real complaints about them. They’re cheap, common, and reasonably reliable. They're made of metal and feel solid, but not heavy to the point of being burdensome. There's also a great assortment of quality lenses that won’t break the bank - both from Canon and from third-parties. FD- and FL- mount lenses will work with these cameras. Neither FD nor FL mounts work on modern Canon DSLRS, hence the cheap prices on the used market (this won't be true much longer since they DO work on mirrorless cameras). Some lenses to look out for: the 55mm and 58mm f/1.2, which are affordable super-fast lenses if you like to play with bokeh. There are also some great super-wides including 17mm and 20mm lenses.
Recommendation? If you’re just starting out with photography (especially with 35mm film), get one. It’ll probably do everything you need it to, and the simplicity of operation can be liberating. If you insist on professional specifications or require an abundance of features, you may want to look for something else. You can certainly get a lot more camera for just a little more money (Nikon N90, Nikon F100, Canon Elan, Canon EOS-3, etc), but as always think about whether or not you'll actually use them in practice.