There's a lot of overlap between what you should have on board in general and what you need for cruising. Here's a list of typical stuff:
Required USCG and NYS items (a bell is a NYS thing).
Food for a couple of days. It's OK to stock up on staples, but pick up perishables as you go along. This is another thing we learned from our earlier cruises. Your boat is your boat, not a supermarket supply ship.
Light Danforth "lunch hook" and heavy plow anchor. We'll discuss anchors and anchoring in detail later.
Heavy mooring pennant fitted with a thimble and shackle (in case the tackle on a rental mooring is questionable).
Wood plugs in sizes to plug each thru-hull.
Strobe lights and whistles to fasten to PFDs. On-deck crew should always wear PFDs at night. A harness and tether aren't sissy gear, either.
Spare everything: clevis pins, cotter pins, winch parts, bulbs, electrical connectors, fuel filter, engine zincs, oil filter, impeller, dock lines, rip-stop tape, hull repair kit (the kind that sets underwater), engine oil, engine coolant, hoses, clamps, flashlight batteries ...
First aid kit, including the Red Cross first aid book.
Autopilot. An autopilot is better than having another crew member, especially when making long passages under power. It can steer a straighter course, doesn't doze off, need a head break or food, and doesn't whine (unless it gets too much sun).
GPS or LORAN. An interface to the autopilot is cool.
Cell phone. It's better than a VHF when trying to contact a club or marina to make a reservation.
Stove fuel.
Bug spray.
Calculator.
Reference Documents
Here's a list of documents commonly carried:
Boat's papers (USGG documentation and NYS registration) and copy of the insurance policy.
The current Eldridge or Boating Almanac for tides and currents. The Almanac also provides a directory of clubs and marinas.
Cruising guide(s).
Up-to-date charts.