A couple of years ago I created a blog post with a link to an 'Unofficial System Center Management Pack Catlog' that a member of the community had put together as a central location to get access to all the download links for non-Microsoft developed management packs. This post proved pretty popular and I still refer to it a lot myself when looking for a particular MP on a deployment.
You can check out this post here: 'Unofficial System Center MP Catalog'
In the last week or so, Microsoft's 'MP Supremo' - Daniel Savage created a new Wiki page that lists all of the existing and soon to be released Microsoft Management Packs along with each and every one of the download links to get quick access to them.
And before anyone mentions it, I know we have the Pinpoint Site that also has a central location for these MP's, but if we as members of the System Center community can ensure that this Wiki is maintained and the links kept up-to-date, then this can be the 'de facto' location for us to get quick access to these management packs.
The new Wiki can be accessed from this link: 'Microsoft Management Packs'
Once again, well done to Microsoft and in particular Daniel and his team for putting the effort into the management pack experience and ensuring that all our queries and issues with them are getting resolved. This type of initiative can only add to the overall value of System Center 2012 in the long run.
**Update April 2015**
I've just come across another useful blog post on SystemCenterCore.com that lists all management packs for both SCOM and SCSM and comes with a really handy MP Elements table and download link for each one.
Check the library out here - http://systemcentercore.com/