Ok, Alli and I have been discussing a couple of visions for expanding orienteering opportunities in the northern suburbs of DC, where there is a fairly high concentration of very active orienteers.
Option 1, geared towards existing orienteers with a view to drawing new people:
A summer weeknight series modeled on the Sydney Summer Series: http://www.sydneysummerseries.com.au/
Have a rotating series of events on, say, Wednesday nights, with start times between 5-630pm during daylight savings time. Keep the format the same each week (either a single course, a score-O, or something similar), and keep overall standings based on X minimum events attended. Use urban or easy-to-get to maps (College Park, Wheaton, Bethesda, Rock Creek (in an ideal world), Cabin John, simple street-O maps, etc.)
Option 2, geared towards attracting and retaining beginners, based on the model used by clubs in Copenhagen when their membership was dwindling a few years back. Pick a single park (say, Wheaton). Have an event at the same time and day each week (say Wednesday between 5-630) all summer. Offer the same set of courses (beginner, advanced beginner, intermediate, advanced) each week and encourage competitors who complete one course to come back the following week and try the harder version. Those completing all four get a free start at a regular QOC event. (Advanced orienteers could take this as speed training, and try to break their own records for the advanced course each week.)