You can rate Photos, Waypoints, Tracks and Routes. Just mark one or multiple items in the List view and select the rate from No rating till 5 starts from the drop down.

Then you can filter or sort the list according to the ratings:

Select one of the predefined filters from the drop down menu, or enter your own filter. The '*' from the keyboard represents one star. You can also filter with <, ⇐, >, >=. For example, entering '>=**' shows all items with a rating of greater or equal then two stars. .