Launched in 2002 by the Cornell Lab of Ornithology and National Audubon Society, eBird provides rich data on bird sightings. Many national wildlife refuges now have an eBird Trail Tracker kiosk where visitors can check which birds are currently being seen in the area, learn more about those birds and add their own sightings. You may also post observations on the national eBird site here.
Here are a few refuges with eBird trackers where you can post your own sightings and look for others.
Ash Meadows National Wildlife Refuge, NV
Edwin B. Forsythe National Wildlife Refuge, NJ
Santa Ana National Wildlife Refuge, TX
Bombay Hook National Wildlife Refuge, NJ