I've done consulting work for numerous ISP's. Everything from porting Linux kernel bug-fixes from 2.0.x kernels back into the unsupported 1.2.x kernels to Cisco router and routing protocol (OSPF and BGP) configuration.
I've done work for other companies including:
Building GNU and ISC applications on old Unix systems. i.e. building/installing GCC, Bash, upgrading Sendmail, building/installing Bind on previously unsupported platforms.
Red Hat Linux server installation, remote administration and long term maintenance, including migrating web servers, email, and web proxy service from NT servers to Linux servers.
Asterisk (VOIP PBX) installation, maintenance, and integration with traditional PBX's.
Since I do work full-time, consulting work is primarily done from home at night or on weekends. To avoid a conflict of interest, I avoid doing work for ISP's that compete with my employer or companies that are clients of my employer unless I was already working for them before their business relationship with my full-time employer.
Prices depend on the type and complexity of the work. Nobody's ever complained about my prices, so I must be pretty reasonable.Contact me at email@example.com if you want to talk about some work.