Many 2.5" SSDs come with adapters, yes. Not all of those adapters have all the right mounting holes though. For example, the A-Data drive I just got has an adapter with holes to match the sides of a 3.5" drive, but not the bottom. I could not screw it to one of the trays in my wife's Antec Sonata case, so it just sits in the tray. That's ok though, because it contains no moving parts so it won't jerk around or make noise.
There are quite a few cases that have 2.5" mount points, typically using the bottom holes. Lian Li, Coolermaster, and Silverstone all come to mind as having at least a few models with such mounts.
I still plan to use spinning disks for documents, pictures, other media, and the Windows swap file (or I may test a small, e.g. 16GB, SSD just for the swap file).