Smaller species that don't need those larger cages will be the "leaf" or "dwarf" cham species such as Brookesia perarmata (armored cham.), Rhampholeon brevicaudatus (stump tailed cham.), and others such as Furcifer cephalolepis (Comoro Isl. dwarf cham.), Chamaeleo rudis, C. wiedersheimi, and Carpet chameleon. The main problems with these are:
they are almost always wildcaught and delicate to acclimate.
healthy ones are harder to find.
because of small size they are difficult to treat for health problems (and most will have some including parasites)
there is a lot less husbandry info available for them.
some species are not as colorful as the big arboreal ones we see.
If you are a beginner cham keeper I would not recommend any of them frankly unless an experienced person helps you set one up very carefully. If you really want to get into chams your best bet is a juvenile (not baby) well-understood species such as the veiled or panther. They do need those larger cages, so if you don't have space for one maybe a cham isn't a good choice. A breeder who has had some luck with the stump tails is Kammerflage Kreations (www.calumma.com)