Creating a tab to link to an external url is quite straightforward. 
Open site setup > zmi > portal_actions > portal_tabs and go to the right hand drop-down, 
leave at CMF Action and hit Add. Add the id (i.e. Blog). Now open the newly created 'Blog'  
and edit it with your info to look like this image

So now that you have entered Title  Blog, Url string:http://foobar.com and selected View under Permissions as well as ticked Visible and saved, you should have a tab which will redirect to an external url!

A bug I encountered with Quills weblog product is the weblog admin portlet being viewable to non-privileged users. This was not a desired result, so off to google I went.
Luckily there was already a diff I could use to patch the offending code in parts/instance/lib/python/quills/app/portlets/weblogadmin.py.

Here is the link to the diff: http://dev.plone.org/collective/changeset/52562/quills.app/trunk/quills/app/portlets/weblogadmin.py?format=diff&new=52562 . Patch the file and the portlet is no longer viewable to non-privileged users.

Various install/build tools such as easy_install, paster, buildout .. grokking {README,INSTALL}.txt and performing manual steps. Products should always have quality documented install procedures at point of issue. covers most of this, yet the conformance should already be in place at the time of Plone 3 stable. Back-porting of packages to that end should also be a reachable goal.

If Plone is to gain wider adoption these would be the stumbling blocks to that end for many organizations.

Testing the quills.remote blogging api via scribefire (Firefox 3 extension). If this posts to my blog then success.