These pages often also provide useful links to other places. Of course, many hams, even packeteers, need a callsign server. The following list links to a few sites which appear to permit open access to the packet network by hams from internet. In every case, you will be asked a name and password. In Spain, Digigrup EA3 provides information and network access.
All pages are in Spanish.
In Massachusetts, USA, KA1THM Internet-Gateway provides network access by sysop permission. Log-in to file an access request. Server telnet, ftp, http, axip, netrom. All users are welcome. There are also several sites which seem to allow access to the local packet network but do not advertise that fact.