Ah, the digital age. It's brought us so much, and without it, I'd be jobless. So for obvious reasons, I'm very appreciative of the existence of digital music. One of its perhaps lesser-known benefits is that with it, any Tom, Dick, or Harry with a sense of rhythm can be a musician. And that's not a bad thing, although certain traditional musicians may beg to differ. Personally, I think anything that adds variety to the creative landscape is positive, although there are certainly exceptions (William Hung? Seriously?) Anyway, if tinkering with audio and making your own music sounds appealing to you, I recommend trying a free demo of Live or checking out the online mixer at JamGlue. Are you hooked yet? Making your own music can be addictive--be careful: before you know it, it's 4 a.m. and you've got to be up for work in three hours.
Once you've determined that this is a worthwhile hobby, it's time to purchase some worthy software and, if you plan on getting really serious, a fast and powerful PC (Macs are great for media manipulation) with a huge hard drive--it's amazing how much space uncompressed audio takes up. As far as software is concerned, is a perfectly acceptable starting point for Mac users, and it even comes standard in iLife ($79, free on new systems). For Windows, try one of Sony's Acid products, or you can invest in Live, which will work on either OS. All of the aforementioned apps include more than 1,000 royalty-free loops each, meaning you can mix, match, and create with impunity. If you tire of those, you can find plenty of sample loops online. Just be wary of what samples you use if you intend to make your music available to a large audience--if you have a popular track, it could come back to bite you in the butt.
Produced something stellar that you want to share? Try Beatport.