Links Menu (Blogroll) »Import & Export Links
You can import links from other systems into your WordPress.com blogroll.
First visit the Tools -> Import page.
Then click Blogroll on the Import screen.
There are two options when importing links. You can import links from an existing blog, or you can import links from a file you have saved to your computer. Links can be imported if they are saved in OPML (Outline Processor Markup Language) file format.
To access the links file for an existing WordPress.com blog, type in http://yourblogtitle.wordpress.com/wp-links-opml.php or if you have exported an OPML file containing links, click the Choose File button to choose that file from a local disk.
To finish, click the Import OPML File button.
You can export your links by visiting http://yourblogtitle.wordpress.com/wp-links-opml.php and then use the Save File option in your web browser (usually by clicking File -> Save As… but the exact wording may vary depending on your browser).