Wake up with kalarm
If you need to ensure that you wake up at a specific time in the morning or just remind yourself of a specific scheduled task you can use a great program called kalarm which allows you to add as many scheduled reminders as you wish by clicking on the "new" button (ctrl-n or actions > new also work) and tweaking the alert as you need it. You can set it to display a text, open a file, run a command or send an email at a specific time that you specify. You can set it up to repeat the reminder every few minutes or whatever period you like and for as many timey you want.
If you simply need it as an alarm clock you can set it to display text (something like "Wake up!"), select sound and choose a sound file to play. Then you simply select time it should play at and the recurrece and you're pretty much done.