I always have this issue because I want to have different ringer volume when in office, at home and while sleep. So I come out with this ringtone volume scheduler, anybody interested in having a try of it???
https://market.android.com/details?id=com.GTechComm.RingToneVolumeScheduler

https://market.android.com/details?id=com.GTechComm.RingToneVolumeScheduler