I second NVU if you are looking for something free that's WYSIWYG.
Should you ever want to edit the HTML markup directly, there are plenty of apps for OS X that let you do that. (skEdit, jEdit, TextWrangler, Taco HTML edit, et al). NVU will let you do this too.
As the other posters have said, there are many freeware applications available.
If you are prepared to spend a little money and want something that is very easy to use, try Rapidweaver. Low cost, template driven, integrated with iLife, HTML editing if you want, a very active user base & forum.
Those are (roughly) in order from easiest to use/least powerful and flexible to hardest to learn but most powerful. I've never used FrontPage, but I have a feeling it would fit in right before GoLive.