Me too. I have a real fascination for this Cambrian period of computing, even though I came into it via the strange world of home computers (Sinclair). By the time I got my hands on business computers, Wintel had won.
I saved an S-100 machine from the skip when I was at school, made by SWTPC. It ran Uniflex, a version of the Flex operating system which was designed for multiple users, based on some Unix ideas.
It worked briefly when I got it but then stopped, and I could never figure out why. In the end, I donated it to this guy http://www.computermuseum.org.uk/fixed_pages/swtp.html who I found via the wonderful alt.folklore.computers newsgroup.
There are tons of fascinating companies like this. Personally I like Connectix. Almost nobody (other than early hardcore Apple users) knows about Connectix, but start listing their products and :o
