HeadSpace2 is an all-in-one meta-data manager that allows you to fine-tune the SEO potential of your site. Visit the HeadSpace page for a video demonstration.

You can configure meta-data for:

Posts
Pages
Categories
Home page
Author pages
Search pages
404 page
You can define:

Tags/keywords, with suggested keywords
Descriptions
Page titles
Custom 'more text'
Site name and site description
Custom themes - change your theme on each page!
Custom plugins - load a plugin only on specific pages
Additional CSS and javascript files
Noindex and nofollow meta tags
Follow/follow on archive, category, page, tag, and comment links
It also allows you to add:

Google Analytics
Google Webmaster
Google section targeting
Mint statistic
103bees
Statcounter
CrazyEgg heat map
Feedburner Stats Pro
Apture
Yahoo! Site Explorer
Microsoft Live Verification
HitTail
Piwik tracking
AWStats tracking
You can also:

Disable visual editing
Disable widgets
Configure first-time visitor messages
Add frame-breaker code
Disable WordPress auto-formatting (wpautop and wptexturize)
Configure memory limits, error reporting, and system timeouts
This is all included in a single plugin. Because of the large number of other meta-data plugins, HeadSpace provides an import function for the following plugins:

Ultimate Tag Warrior
All-in-one SEO
HeadMeta Decription
Jerome's Keywords
lud.icro.us Head Meta
SEO Title Tags
Simple tagging
HeadSpace is available in:

English
Français thanks to Serge
Polska thanks to Jacek Tyc
Deutsch thanks to Mario
Italiano thanks to Gianni Diurno
Bulgarian thanks to Alexander Dichev
Spanish thanks to Juanpa Manson
Russian thanks to Sergey Ryvkin
Danish thanks to Strang Skov and Georg S. Adamsen
Japanese thanks to Yoichi Kinoshita
Brazilian Portuguese thanks to Vinicius Pinto
Dutch thanks to Matthias Houwelin
Simplified Chinese thanks to Rick
Indonesian thanks to Hendry Lee
Romanian thanks to Dragoş Nicolae
Turkish thanks to Omer Faruk
Belorussian thanks to Marcis Gasuns
Ukrainian thanks to Kirin
If you can provide a language translation then please get in contact with the author. A PO file is provided with the plugin and can be used in translating with poEdit.

Download: