If you are reading this, you have one.
On reflection, I realize that that's not true. Many do their web surfing from work or school. Others use wifi at cafes and the like. And I have no doubt there are a few so depraved as to steal access from neighbors too dumb or lazy to protect their wireless networks. If you want a website that is anything more than a toy, you will have to get your own access.
If you don't already have it-
I don't have much to say. If you are a residence, you may have a choice between cable or dsl. Probably you don't, it will be one or the other. If you do have a choice, both work so it comes down to price and customer support. Pick one but don't sweat it because they'll be bought out by somebody in six months and it will all change anyway.
If you are in a commercial building, your building manager will probably tell you who the isp is. If you do have choices they will range from commercial packages from the same people who supply residential service up to dedicated lines costing thousands of dollars per month.
Bottom Line
You don't have much choice and what choice you do have depends on your physical location.
If you are relocating keep this in mind.
Cost: residential: $20/mo+up , commercial:$100/mo+up.
Good luck,
Dave Driscoll