System calls that directly effect the scheduler

exit
fork
vfork
waitpid
wait4
alarm
pause
nice
kill
sigsuspend
getpriority
setpriority
clone
sched_setparam
sched_getparam
sched_setscheduler
sched_getscheduler
sched_yield
sched_get_priority_max
sched_get_priority_min
sched_rr_get_interval
nanosleep
exec

Other system calls that effect the scheduler
open
close
read
write
Anything else that might cause a delay

PROBABLY LOTS MORE TOO