I'm on vacation this week and brought my Necromunda stuff with me to play with my brother (he has Escher, Orlocks, and Spyrers. We bought Necromunda when it first came out (1995!) and we've kept the boxes and all the terrain and all the bulkheads.
We used to do campaigns that encompassed the whole summer, our gangers advancing to hive star status and becoming godly warriors. We're going back to that and I've actually been able to con some of our locals into purchasing models.
Why is Necromunda the best game ever made by GW? The rules are straightforward and flexible, there is plenty of fluff, and the game is basically a roleplaying game on the tabletop.
The rules are free, gangs cost $40. Most 40k urban terrain will work for Necromunda. If you're flush with cash you can purchase the original Necromunda terrain on ebay.
Yakromunda is a great way to track your gang and record battles. It is a cutting edge website that allows you to do everything when it comes to recording all the advances your gangs get.
Check out the free rules, grab a gang and get started! Here is a photo of my brother and I playing last night.