Canoo : Dictionary & Grammar for German - Enter a German word in the search bar, then choose an option including 'Rechtschreibung - Spelling Reform' 'Flexion - Conjugation/Inflection'.
Duden : Spelling Reform Examples - Use the alphabetic table 'Beispiele von A bis Z' to find a specific word you are unsure of such as 'D' for 'da' (new spelling is 'dass'). In German.
Redewendungen und Redensarten - German interface. Take any German word - 'Kopf', for instance. Enter it in the search bar and receive a page of 'sayings' (Redensarten) and 'examples' (Beispiele).