There is no way to do that within Chrome yet. But I've heard that you can do it using an extension of Firefox that can read the database that Chrome stores its bookmarks in.
- Download SQLite Manager Mozilla Firefox Plugin
- Run SQLite Manager from within Firefox (Tools > SQLite Manager)
- Click on Database, and then Connect Database
Windows XP: C:\Documents and Settings\<USERNAME>\Local Settings\Application Data\Google\Chrome\User Data\Default\History
Windows Vista: C:\Users\<USERNAME>\AppData\Local\Google\Chrome\User Data\Default\History
- Click View > Create View, name it bookmarks and enter SELECT * FROM urls WHERE starred_id >= 1 then click OK.
- Click View > Export View and click OK, use the next dialog to save the file to wherever you would like.