I've been working on a nice little update to our attack database on PokemonDb. Firstly, I have spent a lot of time writing more detailed descriptions for more moves, so attacks such as Blizzard, Natural Gift or Leech Seed now have full details on their effects.
Secondly, all moves now have a graphic indicating which Pokemon the move will hit or affect. They show a triple battle layout, but just ignore the two far right places for double battles. For example, Rock Slide hits both opponents in a double battle, or adjacent opponents in a triple battle:
Finally, there is a new filter page in the move section that lists just the moves hitting multiple Pokemon.