You should check out 280north's Atlas. <a href="http://280atlas.com/" rel="nofollow">http://280atlas.com/</a>  It's still in beta, but you can get access to it by preordering it (highly recommended).<p>WebKit's Web Inspector is quite awesome -- Apple actually has bankrolled a few full time employees to work on it, and many more contributors have been hacking away at it for quite some time.  In my opinion, it is the best example to learn HTML 5 best practices from (it is written in HTML 5 itself).<p>FireBug is also great (I prefer the WebKit Web Inspector myself, since about 1 year ago, due to its rapid updates) but FireBug is quite excellent.<p>Apple also provides some a rudimentary IDE called Dashcode, which I don't really like, but might be helpful for others.  The OS X dashboard has been 100% WebKit / HTML 5 powered for quite some time.<p>Not to say that these are necessarily better than Adobe's dev tools, but the writing is on the wall.  The awesome thing is that all of these I have mentioned, with the exception of Dashcode, are open source and rapidly developed both by full time employees of various interested companies and the community.