Commercial IP Address Management (IPAM) products are odd beasts. They offer comprehensive feature sets, but most are Windows-only and priced in the five-figure range, with a license cost based on the number of managed addresses.
Unix and Linux admins who don't have five-figure budgets are used to writing their own IPAM tools using standard applications like PHP, MySQL, Nmap, Netcat, fping, Kismet, sed, awk, snmp and gosh knows what else. You can easily cobble up a pretty good network discovery and reporting system, but assembling a unified controller that manages name services as well is a fair bit of work. Fortunately, a few prefab open source IPAM application are worth a look.
IPplan is mature and well-maintained. It is yet another PHP-based application that supports pretty much any database you want to use on the backend. It is well-documented, has a pleasing, well-organized Web interface and can be used for DNS management. It imports network definitions from routing tables as well as data from tab-delimited and XML files, finds free address space, supports VLANs, has an audit log, and handles NAT. IPplan's one downside is it uses PHP4, which is dangerously old and insecure.
IP Reg is also MySQL/PHP-based. It's so new, it squeaks. It has a similar feature set to the others, plus it displays addresses in use in colors for different network segments.
Another option is to use these tools as inspiration for your own custom solution. All three are licensed under the GPL, so you can re-distribute your modified versions or contribute back to the original project, a nice thing to do because the Unix/Linux world needs more good-quality IPAM applications that integrate gracefully with name services.