POP3/IMAP/SMTP Servers (Mail Servers):
ArgoSoft - http://www.argosoft.com (free under personal license)
hMailserver - http://www.hmailserver.com (free, open source)
Mailenable - http://www.mailenable.com/ (trial)
FTP Clients:
WS_FTP - http://www.ipswitch.com/products/ws_ftp/index.asp (trial)
Filezilla - http://filezilla.sourceforge.net (free, open source)
FTP Servers:
WS_FTP - http://www.ipswitch.com/products/ws_ftp-server/index.asp (pay first)
Serv-U - http://www.serv-u.com/ (free for personal use)
Filezilla - http://filezilla.sourceforge.net (free, open source)
Cerberus FTP - http://www.cerberusftp.com (free for personal use)
DNS Servers:
Zoneedit - http://www.zoneedit.com (free for the first 5 domains)
FreeDNS - http://freedns.afraid.org (free subdomains)
IM Servers:
NewAge Server - http://www.serversoft.us.to (free for non profit use)
Jabber? - http://www.jabber.com/index.cgi (free?)
Other:
DNSStuff - http://www.dnsstuff.com (looks at your DNS servers, and says if there are problems.)
Note: I suggest this thread stay here because the place where people are asking for this stuff. Ill post more later ;). Also post some if you know more.