openstreetmaps ftw. Get that, turn on cartographic overlays (outdated scans but still useful), aerial imagery, download and import nhd data, pull up ngs website, and enjoy. Help us map rivers! Even better if you can do an actual ground survey w/ gps.
I spent way toonlong mapping our houses in my neighborhood. It's always funny to see my work on apps, I'm like shit that street is missing houses I need to get on it.
yeah, it's addictive, I started with sidewalks in my neighborhood, and before I knew it, I was mapping parking zones, fire hydrants, trash cans, benches, traffic signals, speed limits, turn lanes...
What's the best tool to map points? I walk my dog and would love to quickly drop a pin for a sewer grate or fire hydrant? Is there something I can do mobile?
btw NHD data tends to be too large for JOSM to handle... my one complaint about JOSM, I feel it could be more memory efficient. Qgis can be used to process and extract large datasets, just split them up into several files per state. (You also need to merge the source files.) But it's totally worth the pain, because you get a lot of rich, high resolution data.
Depending on where you live, your state or city might also have open datasets available.
Be sure to check out the osm wiki! For editing, you can use their web viewer, but I personally prefer JOSM for more advanced work. Vespucci is a great tool for mapping on your phone.