Properly there's tons of free services that you can monitor your stats and which sites has refereed your visitors and which keywords they're using to find you, I personally don't really check it that much but I track my blog visitors using 3 monitor services, the first one is using the blogspot's native tracking, and it's not that cool but helpful to track visits to each individual post.
Recently I signed up with http://www.clustrmaps.com which gives you a nice map layout of your visitors and it's a free service too, you'll find it in the right hand side of my blog. it looks cool, but can you tell me how these 2 guys are accessing my blog? on a cruise ship or on a boat!! first let me thank him for checking my blog out, but I'm just wondering...
My third tracking is using http://webstats.motigo.com it's also a free service and gives you more statistics than clustermaps and also layout the visits on a map, and I still see the same guys 2 and someone who's totally in the middle of the ocean !!
Really it's helpful to know where you visitors are coming from and which posts they're looking for, and to some people who place ads to generate revenue to their blog, it's a starting point to tweak their posts and their blog to attract more visitors.
Hope that helps someone and please contact me if you're that man in the boat!