In addition to what Rob lists, I'd add:
I'd recommend a Delta over a Fortress as a spare anchor. The Delta will probably set better and hold better than a Fortress, especially in shifting current/wind conditions, which will often cause the Fortress to break out.
Checking and replacing any flares that are expired is also something you should do every spring. I highly recommend that you get SOLAS grade flares rather than just USCG flares. The price difference isn't all that much but the difference in performance is phenomenal. If your current flares are SOLAS grade and expired, keep them as backup flares... they won't help with regards to USCG inspections, but most will be good far past their expiry dates, and having extras in an emergency might make a difference.
Check the batteries in the flashlights, CO detector, Propane detector on your boat. If you use propane, you should have both a propane and CO detector installed.
Check the water level in your batteries, if they're wet-cell. If low, top off with distilled water.
With respect to the inflatable PFDs... I would manually inflate them and let them sit overnight to check them for leaks while you're replacing the arming kit and cylinder.
Check your USCG documentation and renew it if necessary. Same with your Ship's Station Radio License. The USCG Doc needs renewing every year, and is free, the FCC SSRL needs to be updated every ten years IIRC, and can be done via the www.FCC.gov
Check the bulbs in the navigation lighting, and make sure they're up to spec. If the bulbs appear cloudy or smoky, they probably need to be replaced, since the appearance is usually caused by tungsten plating onto the glass from the filament.