So I found out what has happened to skulltag and as to why it's so hard for people to find servers. Skulltag is finished. The ENTIRE STAFF working on skulltag (except the creator, Carnevil) left Skulltag to form another online multiplayer port called "Zandronum" and it's being built on the latest devbuild (alpha) of Skulltag, 98e.
http://zandronum.com/I don't know what I'm going to do, because I'm loyal to Skulltag, it's better than EVERYTHING else, but, I have a fix for you needing to get your skulltag working properly. You need to update your skulltag master server address to master.zandronum.com:15300 in either doomseeker or Internet Doom Explorer (IDE)... You need to do it so that you can play online properly. You'll still be able to connect to servers and play as normal... for now. You'll find the MASTERSERVER addresses under Configuration>Engines in DOOMSEEKER and under Options>Master Server Address in IDE. In IDE ONLY change the masterserver address for SKULLTAG. Leave Odamex and Zdaemon alone.
So as of June 3rd, 2012, Skulltag is currently no more.
http://www.skulltag.com/itends/Oh dear god... what to do... *cries*
(Oh, carnevil's new project is
http://www.wrackgame.com/)