How to set services start priority in OpenSUSE 11.1?

the folder /etc/init.d/rc3.d contains all services for your install.
looks something like this:
S01acpid S07kbd
K01cron K02fbset S01dbus S08ntp
K01dahdi K02haldaemon S01earlysyslog S09dahdi
K01microcode.ctl K02kbd S01fbset S09network-remotefs
K01network-remotefs K02ntp S01microcode.ctl S09nscd
K01random K02sendmail S01random S09splash
K01smartd K03nscd S02haldaemon S09sshd
K01splash K06syslog S02network S10sendmail
K01splash_early K07earlysyslog S03syslog S11cron
K01sshd K07network S04boot.clock S11smartd
K01stopblktrace K08dbus S05splash_early S12stopblktrace

If I wanted Sendmail to start before Dahdi, I would rename S10sendmail to S08sendmail.imopro

there is an rcx.d for each runlevel 1-6. Some of these can't really be changed, but you'll be warned if that's the case.

If S09ypbind and S10avahi-dnsconfd. And I want service sshd run between ypbind and avahi-dnsconfd. what should change service sshd?

you would have to rename S10avahi-dnsconfd to S11avahi-dnsconfd and set up sshd as S10sshd.

But I can see several services have S11xxxxx the same. Which one will run before another. Can we put S10.5?

No. The Sxx priorities are symbolic links that process "Alphabetically" (ASCII Alphabet). So if you have 3 S11 priorities, you can make a new first priority by making it S11aaprocess.