The "newbie links" at the top of this forum are a good place to start... the "top model" mics probably cost more than your bass, but there are many choices in the $100-300 range that will do the job. I have a Shure SM-57 and also a bridge wing pickup as Nagrom recommended. The pickup took a little patience to fit, but I like that it's easy to put on and take off since I mostly play without the amp or with a mic and use the pickup only when those options won't work.
Whether a mic or pickup is the better choice depends a lot on what kind of music you're playing, where you're playing it, and how loud. As volume levels go up it becomes more difficult to use a mic without feedback so for "stupid loud" gigs (ie electric guitars and drums) you'll want a pickup . If I've got to amplify, I like the sound of my bass much better through a mic, but I like the sound I get using a pickup a whole lot better than the sound of feedback.