There is a relatively new, open source project on sourceforge called Office Manager – Medical Edition. It was designed to be as easy to install and use. While it has a good deal to go to be as feature rich as many of the other software packages, it is MUCH easier to install and use. It has patient management, inventory management, rudimentary accounting, claims management, HCFA 1500 forms, insurance management, Point of Sale to integrate with insurance billing, scheduling and administration. It works on Linux, of course, but also mac, windows, and pretty much any GUI operating system that can run java. Michael Lee (myself) is the sole author of the program and is looking to find a way to work on the program full time. It was developed on my own time to support a group of doctors. Check it out.
http://sourceforge.net/projects/office-manager/