Guide to adding the My SharePoint Sites Web Part to your site.

What this Web Part does is aggregate any and all content that you have authored/uploaded (from across multiple sites within your site collection), and presents that content to you in a cleanly designed Web Part which uses a tabbed user interface. 

So how can you get a My SharePoint Sites Web Part?  It's simple.  First, from within the site where you want to create the Web Part (I added it to my My Site which, come to think of it, may in fact be the most logical location for this Web Part), select the Edit Page menu option from the Site Actions dropdown button:

On the resulting Edit Mode display of your page, choose the Zone where you'd like to add the Web Part.  I'd recommend adding it to whichever Zone provides you the most width, since that will give you room to grow in terms of adding tabs for multiple sites.  Once you've chosen a Zone, click the Add a Web Part bar in that Zone:

In the resulting Add Web Parts popup, locate My SharePoint Sites listing, noting that you may need to scroll and/or expand certain areas to find it.  I found it under the Content Rollup heading on our portal.  Having located it within the list, click the associated checkbox for the Web Part:

Once you've placed a check in the checkbox, and clicked the Add button at the bottom right of the popup, your page will refresh (in Edit Mode) with your new My SharePoint Sites Web Part in place.  I suspect that, as was my experience, you'll find several default site tabs will appear automatically, with the tab for the site on which you've added the Web Part preselected: