ChanServ - Channel management, prevents take overs and the like. Use NickServ to register an account. /cs help for help.
NickServ - To register an account and your nicknames thus preventing others from using them. /ns help for help.
AntiSpam - Does as it nick states, prevents spam.
MemoServ - If a user is offline and you want to send him/her a message, you can leave one using MemoServ. /ms help for help.

ReplayIRC uses the x3 services from evilnet.