[Now updated for 2015!]

systemdReplaces init, cron, inetd, udev, locale, acpid, atd, su.
systemd-journaldReplaces syslog, klog.
systemd-logindReplaces getty, login, xdm. (*)
systemd-networkdReplaces ifup, ifdown, tcpwrapper, hostname, dhcpd.
systemd-journal-gatewaydProvides HTTP server for systemd-journal.
systemd-timesyncReplaces NTP.
systemd-resolvedReplaces resolvconf, bind, powerdns-recursor, dnsmasq.
systemd-automountReplaces autofs.
systemd-readaheadNo longer supported because everyone who matters has SSDs.
systemd-machinedReplaces VirtualBox, VMware. (Coming soon.)
systemctl-catReplaces cat. Really.
systemd-udevdReplaces udev.
systemd-firewallReplaces iptables.
systemd-journal-remoteReplaces logstash/elasticsearch with a new logging protocol over HTTP.
gummibootTo be incorporated, replacing grub.

Also, here come the security vulnerabilities:

…systemd-resolved does not implement any of the hardening recommendations of rfc5452

(*) OK, so it’s a bit more complicated than that. Eventually the plan is to get rid of X11 for Wayland, but currently X11 is still allowed. However, systemd is part of the PAM configuration now, and systemd starts your X session with display manager and window manager. So far login and getty still service legacy non-console ttys.