In original blackberry OS, you can only set a alarm in clock, SmartSoft has designed MultiAlarm, It can set as many alarms as you like, the software uses Rim api, so there is no background thread to work, so less burden for device cpu and memory. It support many notify methods such as music, LED, vibrate. It consider about power on your device if alarm should be fired.
AppWorld link: appworld.blackberry.com/webstore/content/screenshots/41860?lang=en
If you can not download from app world, you can download it from Mobihand or crackberry shop.
Now there is price discount. 40% off, only $2.99, and You can download it free and try for 3 days.