I searched but could not find any topic about free apps for Surface Pro. So, on mine (64GB) are
Social: Tweetro, Facebook Touch
News: Discourse, USA Today, News 360, NBC News, News Bento, BBC News
Weather: AccuWeather, WeatherBug, Weather Flow
Game: MS Solitaire, MineSweeper, Pinball FX2, Armed, Radiant
Utilities: Remote Desktop, OneNote MX, TeamViewer Touch, Kindle, MyExplorer, BookReader
Shopping: XE, Digital Folio, Ebay, Amazon, Newegg
Entertainment: TrackSeries, TuneIn Radio, Netflix, Hulu Plus
Other: Learn Windows 8, StumbleUpon, Khan Academy, Wikipedia
Social: Tweetro, Facebook Touch
News: Discourse, USA Today, News 360, NBC News, News Bento, BBC News
Weather: AccuWeather, WeatherBug, Weather Flow
Game: MS Solitaire, MineSweeper, Pinball FX2, Armed, Radiant
Utilities: Remote Desktop, OneNote MX, TeamViewer Touch, Kindle, MyExplorer, BookReader
Shopping: XE, Digital Folio, Ebay, Amazon, Newegg
Entertainment: TrackSeries, TuneIn Radio, Netflix, Hulu Plus
Other: Learn Windows 8, StumbleUpon, Khan Academy, Wikipedia