I have a '99 SL2 that's been running fine up until this morning. When I turn the ignition, I get lights & power, but it doesn't attempt to start. It just makes a clicking noise.

I'm assuming the battery's fine, since the alarm, lights, radio, etc works. I've checked fuses for the the ignition system and they appear to be fine.

Any other suggestions before I call for a tow to the dealer?

Just because you are getting lights when you turn the key does not mean the battery has enough power to start the car. I suggest trying to jump start it.

I'd suspect a bad battery too. This would be especially true if it is the original one too.

I think you have a bad starter. if you get lights then the battery has power. When it is making the clicking noise, go under the car and hit the starter with a hammer and see if it starts then. I would say that it sounds like your plunger on the starter isn't engaging.

make that a rubber hammer...you dont want to dent or destroy it...

I think you have a bad starter. if you get lights then the battery has power. When it is making the clicking noise, go under the car and hit the starter with a hammer and see if it starts then. I would say that it sounds like your plunger on the starter isn't engaging.
That would be one way but I know the Delco batteries have been having major problems of dropping cells. It would look normal until heavy load.