Efficent allocation of sub blocks from a CIDR allocation

Does anyone have any suggestions, or example code, on how to handle
allocation of sub blocks from a CIDR allocation. Previously Connect
has allocated a /24 as the minimal block but now the APNIC have
advised that they do not consider this allocation policy to be
efficent as defined by RFC 2050 and so I am trying to recode our
procedures.

I would like to find (or else write) some code that will "optimally"
allocate sub blocks and generally manage our allocation (so I can
return blocks to the pool when customers leave etc). For routing
convenience (optimisation) I would like to also collect together sub
/24 allocations for specific POPs so that we don't need to announce
all the sub /24 blocks to multihomed customers, peers and providers.

Any ideas? Or pointers to other people to ask (the APNIC have been
silent on the issue after requiring us to do it before they will issue
us another block).

Mark.