hmmm... judging by your handle I think I've got this covered.
Downtown is where you will probably want to spend a lot of time. Cricket's, Austin's on the Ave., and Trueff's are all pretty good bars.
On Baylor's campus there is a small bar called the Dancing Bear Pub, it's pretty cool, but a quiter atmosphere.
There is always George's and there is a new George's in Hewitt as well. If you're looking for more of a dive you could head to the Crying Shame.
I've been to Salty Dog once and it was pretty cool inside, there just weren't many people. It is located in a shopping center off of Valley Mills.
If you want to go a little out of Waco you can head to the Hog Creek Icehouse, they almost always have music.
If you're looking for more music pick up a Waco Trib for the week. I can't remember what day, but they usually have a section with upcoming events and bands playing.
Hopefully that helps out a little.