There are a few really interesting mailing lists which I enjoy reading from time to time, if you do start subscribing to some lists then you should setup rules in your mail client to manage the mail or they can become overwhelming.

Cisco-nsp – This is a mailing list for people using Cisco in a Network Service Provider environment, it gets approximately 8 new posts a day and around 40 replies to those 8 posts. There are lots of interesting problems posted which are being experienced in the field. This is my favorite list by far and I try to read through some of the strange issues once every few days.

NANOG – Is the North American Network Operators Group this is for network operators primarily in the US but is used by people in other countries. They also have meetings in the US. It gets around 5 posts a day and 15 replies to those posts.

RIPE – RIPE (Réseaux IP Européens) is a collaborative group which is open to all interested parties in the development of the Internet in Europe. They have meetings every 6 months which is when most of the work gets done, they are organised into working groups, the mailing lists have very low traffic but its fun to be part of the community especially at RIPE meetings. RIPE & the RIPE NCC (Network Coordination Center) are separate entities but very closely related, the RIPE NCC is the Regional Internet Registry (RIR) for Europe, similar groups exist in other geographies such a IANA, APNIC, ARIN, Arfrnic, & LACNIC.

IETF - The IETF has lots of mailing lists and some have massive amounts of posts daily, trying to keep up with the IETF general discussion feels like a full time job. These lists are generally revolved around standards development.