We're really excited about this newest app that's now live in the HubSpot App Marketplace: Blog Importer from TJ O'Connor. This app allows you to import blog posts into your HubSpot portal from any Wordpress, Blogger or any RSS/ATOM feed. Basically, if you can export your blog from your current blogging platform in XML format, then you can use this app to import your blog into HubSpot and take advantage of the HubSpot blog platform.
To use the app, just install it from the App Marketplace (under Community -> App Marketplace), then searching for "Blog Import" and hitting the "Install" button. Run the app by clicking on the app's link in your Community menu. It should take about 5 minutes to setup the import, and then your posts will be imported in real-time (5 - 10 seconds per post). You'll see the posts that are being updated as the app does its work. After importing, you will need to review each post and update any relative links and image references to make sure that your posts look the way they should look.
After your import has completed (this part is awesome, BTW) the app will give you an output of all of your 301 re-directs that you can then take and put into HubSpot (under Settings -> URL Mappings). This will ensure that your SEO credit from your blog will retain itself through your blog migration process.