Currently the smallest ASA appliance is the 5505 which has been in the market for several years with millions of installations worldwide. This small, passively cooled firewall still receives all the latest ASA software upgrades and features and has been a favorite firewall appliance for SOHO or Small/Medium Businesses.
The ASA 5505 is equipped with 8-port 10/100Mbps switch ports with 2 of them having Power over Ethernet (PoE) capabilities. However, the 100Mbps started to be a bottleneck for some networks.
Cisco is finally planning some new lower-end models that will be the successors of the 5505. There is no official public information yet but I have heard that the new models will be the ASA 5506-X (with 5506W-X variant) and the ASA 5508-X.
EDIT: The ASA 5506-X has been released since 2014. Here is a basic configuration guide for 5506-X.
The new models are supposed to have the FirePOWER engine and also equipped with Gigabit ports. The FirePOWER module (most probably will be a software module on the low-end modules) offers next-generation firewall services, including Next-Generation Intrusion Prevention System (NGIPS), Application Visibility and Control (AVC), URL filtering, and Advanced Malware Protection (AMP). However, I don’t know which of the above services will be able to run on the 5506-X / 5508-X and what the licensing and other requirements will be.
Again, there is no public release info from Cisco yet but stay tuned and will be announced pretty soon. That will be an interesting development for the ASA family of products.