I've dove about a half dozen shore sites on Aruba and as mentioned earlier, these for the most part are different from Bonaire as they are shallower with not as much reef life, but a lot of fun none-the-less. There are some shallow sites like Malmok (near the wreck of the Antilla) and Boca Catalina near Palm Beach. These are mostly patch reef in shallow water. The best shore sites are of on the south side of the island and require a rental car.
Pos Chiquito, (also known as Puerto Chiquito or Rocky Beach) which is a little over half way from Oranjestad to San Nicholaas is hands down the best spot that we shore dove on Aruba and equalled any of reef dives we did by boat. It is where all the local dive shops take their open water students. When we were there this December, the vis was 60' to 70' and a toasty 83f with mild currents which changed directions day to day. The reef is large and fairly healthy, starting in about 10' to 15' of water and slopes down to over 100'. It was the closest site I found to an average dive on Bonaire and requires only a 50 to 100 yard swim from shore. Its definitely worth a few tanks exploring (I could have spent a week on it), and you can ask any dive shop for directions.
Mangel Halto is a nice shore dive just north of Pos Chiquito, but it requires either a long surface swim (about 200m) or as I did it, a long walk in waist deep water before putting on the fins. Its worth a tank. Baby Beach is at the southern tip of the island, past San Nicholaas and the refinery. You also have a long surface swim or walk in chest deep water and there are typically strong currents outside of the reef wall. Its worth a tank.
De Palm Island is another very good shore dive, but they have made this a very expensive option as it is now around $55 per day cover charge to get on the Island and I don't know if they charge more for tanks once you get there or let you bring in outside tanks now that this is a resort. We last went in 2000, before they started charging the big bucks.