Managing allocatiions out of a CIDR block

I am trying to rewrite the system that we use to allocate blocks from our provider blocks to customers. Previously the smallest block we allocated was a class C and so this process was pretty easy but now I want to be able to optimally use our allocations and allocate blocks down to a /30. Does anyone have any ideas, or code, that will manage multiple CIDR blocks and keep track of the currently unused parts of the block and given a requirement find an appropriate allocation (while not fragmenting it like crazy). It would be also useful if it could collect together POP specific blocks so that, for example, two parts of the same class C were at the same POP. Ideas, suggestions? Thanks, Mark.