Yes. It is easy for you to import your blog content from a variety of other blogging platforms, including Blogger, Blogroll, Blogware, DotClear, GreyMatter, LiveJournal, Movable Type and TypePad, and others. Simply log into your WordPress.com blog dashboard, then go to Tools -> Import, choose your previous platform and follow the instructions presented.
You can also easily import content here from another WordPress.com or WordPress.org blog or web site (choose the WordPress option). This option allows you to import posts, pages, comments, custom fields, categories, and tags from a WordPress export file.
If there is no importing tool for your particular platform, you will need to try and convert it into one of the accepted formats so that you can use the proper importer.