I am looking for a small computer (preferably with Linux, but as long as it can be programmed I am happy), that comes in a casing and has at least one RS-232 (9 pin D-SUB) connector and an ethernet port.
Power consumption is not an issue, it will be grid-powered, size and price are important. Also, it is for a commercial application, so availability is also important.
I have found the NanosG20, but I was wondering if that is a good choice, or that others are perhaps available.
One solution with which I am familiar is to buy an older thin client such as the HP t5740e WES.
This machine is low-power and fairly cheap, but it has your RS-232 and ethernet as required. It also has some other neat perks, like 4gb of internal flash storage (not as fast as a conventional SSD for sustained reads/writes, but should make for a good swap partition or even OS partition, since it is low-power and has good seek times).
The biggest downside here is that it runs on the Atom N280 chip, which is a very low performance single core x86 processor with hyperthreading. A headless or openbox/i3/LXDE-based linux would be the best match for its capabilities, and don't ask it to do to much in the way of running a program. I've run old dosbox games on it just fine, but that's about the limit.
Another possible solution, if you need even less processing power and more cost savings, might be the ALIX.3D2. This is a dev board which supports linux and runs an AMD Geode x86 processor at 500mhz - very low power, very low performance, but also very small and rather inexpensive - though you'll have to source the enclosure and power supply as well, of course.
