All the suggestions I'm going to make - and much more - can be found in the wiki - specifically
http://wiki.radioreference.com/index.php/Delmarva_Milcom_Monitoring
Topics would include:
Potomac Consolidated Terminal Radar Approach Control (KBWI UHF frequencies - ignore the civ air freqs)
You will notice that these freqs are often busy with controllers echoing traffic from the civil air side. This is normal; they're keeping the mil folks aware of what traffic is in their vicinity.
Andrews AFB
Martin State Airport
Always keep
260.9 in the rotation. This is a NORAD (HUNTRESS) frequency that is commonly used not only during exercises, but at times is also used when pilots are testing things such as the laser sparklers that warn pilots when they veer too close to restricted areas (like around the White House). It is not busy all the time, but when it is, it can be rather interesting
255.4 - Nationwide Flight Service Frequency Here you will note flights calling in to get weather information, ect. for their destinations. Again, this isn't the busiest of freqs but when you hear something here, pay attention. With a little careful listening, you will be able to get an idea of flights traversing (or perhaps leaving) the area.
360.7 This is the Washington Center SWANN sector freq for our area. Again, civil flight information is echoed from
134.5
All these freqs are in
AM mode
That should be enough to get you going. You will need a good outdoor antenna (with the right coax, of course) if you want to get into this game. While your 396 will handle the milair stuff, the other scanners won't - however, both Andrews and Martin use civil air freqs (118-136 mhz) - you will hear commercial flights checking in there, but you will get a good idea of what is traversing that area.
73s Mike