Panics Coda - never found anything close on Windows/Linux or OS X.
TextMate also very good especially if your programming in Rails.
Coda is THE main reason I run a Mac. Spent a long time in Dreamweaver until I realised I had not opened the WYSIWIG editor in about three months.
My advice use whats easiest for you - but if you want to build web apps, code in a team and use OOP techniques learn to hand code. It's worth the pain of having to google every html element.
Windows : Dreamweaver, Notepad++ and MS FrontPage
Mac OS X Leopard : Panic Coda (The Best of all the things)