As mentioned in the meeting yesterday - it is possible to get second hand rack mounted servers for about 15k from Computer Planet @ Visions Plaza on Mombasa Road. Specs should be around PIII, 512/1024MB RAM, 40GB, dual ethernet cards, some have dual processors. - should be brand names like IBM.
I suggest that for anyone who wants to get hold of one - get to pass word around so that a group can go there and negotiate for lower prices (e.g. <10k clear="all">
Then hacking on stuff like asterisk etc (and for those guys who'd want to starting thinking of colocation) can start in earnest