Within the Wellington Green mall in Wellington Florida there is a replica mammoth skull tucked away in a corner of the lower level; the entrance to what looks like a very strange store. Inside is the Palm Beach Museum of Natural History. They have a triceratops, a saber-tooth cat, mammoth tusks and a set of teeth from mastodons through elephants for comparison, and in the back a small display on the evolution of the horse.
The tour of this maybe 600 sq. ft. museum includes a 5 minute discussion on how Darwin and his students used horses to understand evolution because they had complete sets of the skeletons to study. Once everyone else left there was an opportunity to talk with the director and it turns out he's looking to move into a larger space and have an entire exhibit, with skeletons!, from hyracotherium to modern equus. They have monthly talks from notable archaeologists, anthropologists, and paleontologists. If you ask and they have it handy they'll pull out their Dakota Raptor bones and show you the ligament connection scars from the feathers!
Palm Beach Museum of Natural History. Admission is $5 and it's worth every penny.
Bryy -- yes, that's really great, especially because per your description it does not sound like they're selling actual fossils, which is unethical (they can sell casts or replicas however, plus books, educational videos, T shirts and whatnot).
If you're talking Florida, there are a couple more worthwhile visits in addition:
(1) The University of Florida at Gainesville has the Florida Museum of Natural History. This represents the University's large collection of the fossil mammals of Florida, which is definitely a must-see as it is a somewhat unique collection.
(2) The Osteological Museum in Ocala, sponsored by Skulls Unlimited Inc. They have a wonderful collection of mammal skeletons, including horses, presented as full mounts. Go with a sketchpad for a wonderful opportunity to familiarize yourself with the horse's internal structure and compare that to other mammals and other vertebrates.