Try ipplan/iptrack on sourceforge. I've been using it for the past 3-4 months without a problem.
It allows you to split and join subnets easily. Assign groups of IPs to multiple locations. End users can submit requests for IP addresses.
You can also configure it to scan certain blocks of networks for DNS / ICMP Ping responses and to auto-populate your database. It can even use SNMP queries on your routers' and switches' ARP/CAM tables to populate the DB too.