I have been wanting to write this for some time and finally found the time last week - an AddIn for visual studio which allows you to edit SharePoint content. I had started this several times, initially trying to mimic SharePoint Designer by using
author.dll...this was complicated and took far too long to get anything useful to work. I also tried using the SharePoint web services with some success, but again they can be cumbersome and still didn't provide all the functionality I required. So for the SharePoint Developer Explorer I have written a web service which provides all the functionality I required.

It has its limitation...currently it only allows the editing of text files and the WYSIWYG designer doesn't work, but I only really want to edit layouts, master pages, CSS & XSL.
Here you can see it editing blueband.master.
It has context menus allowing you to check-out, check-in and publish content.
Because the explorer has its own web service I can get access to anything on the server and so the add-in provides some additional information about the site. Here you can see the explorer giving access to the SharePoint log file. You may also notice that you can get access to the content types (XML schema) for the current site.
Its by no means finished, it still allows you to attempt things you aren't allowed to do, the icons are rubbish and some of the error handling needs polishing. However it does work and I have been using it to edit sites with no problems.
I plan to finish it off over the next week or so, but was hoping that I could tempt a few people into beta testing for me, in the hope that we get the obvious problems out of the way. I'm not asking for an exhaustive test of the functionality...just to make sure you can install it, connect to a site, try some functionality, make some suggestions and report any bugs.
If you want to try it out please use the contact form and I will email you the install as soon as it is ready (couple of days).
I have add a new post where the AddIn can be downloaded.