If you haven't purged any services they all got added to the runlevels and started when the packages were upgraded. Don't ask me why it is so, I simply don't understand the reason.
The easiest way is to do cd /etc/rc5.d and do ll and check for todays dates,
those probably got added and you can do update-rc.d -f servicename remove to stop them from starting at boot.
To just stop them do /etc/init.d/servicename stop
Post here the output of ll if you don't know which services you can do without. The ones you know you won't need can be purged with apt.