The link in the comments helped me get here but sys.extended_properties is a per database view. So the properties for each database are contained in the database. This worked though.
CREATE TABLE #EP (DatabaseName varchar(255), PropertyName varchar(max),
PropertyValue varchar(max))
EXEC sp_msforeachdb 'INSERT INTO #EP SELECT ''?'' AS DatabaseName,
CAST(name AS varchar), CAST(Value AS varchar)
FROM [?].sys.extended_properties WHERE class=0'
And if you want all the databases and just properties where they exist.
SELECT db.Name, #EP.PropertyName, #EP.PropertyValue
FROM sys.databases db
LEFT OUTER JOIN #EP
ON db.name = #EP.DatabaseName