The market on the NOOKcolor, even if it looks like the new market, will only show applications that conform to the Android API 7 API level (2.1 and below). Android 2.2 apps all conform to the Android API 8, so they won't show up on your nook unless you drop FroYo onto it.
Three things have been known to help with listing more apps:
1. Turn your nook sideway to landscape and more apps should show up.
2. Use Nook Color Tools:
Settings > Applications > Manage Applications > (Filter by all) Market > Clear Cache (NOT DATA!)
Settings > Applications > Manage Applications > Google Services Framework > Clear Data > Force Close
3. Install the new market apk: Use Root Explorer, changed the System/App folder to R/W and then you will be able to upgrade the current Market to the newer market apk. With the new marketplace all apps are showing without needing to turn the screen to landscape.