If you want something with more features than mapsource, consider QGIS (http://www.qgis.org/
). Be aware, this thing has a learning curve but is capable of providing world class maps (think open source ArcMap for capabilities). You can import every map file I have run across, and export any layer to pretty much any format (including Google Earth KML). If you grab PostGIS (postgres SQL GIS enabler) you can also store you maps in a DB.
To display Google/Bing/OpenStreet maps/sat images in layers while you review or draw, grab the OpenLayers plugin (qgis has a long list of plugins) then choose the provider(s) layer - you can add all if you so choose. I keep 5 different provider maps as layers but typically only have 1 enabled at a time.
Another thing to consider for maps is some-- not sure how many --states have GIS repositories. These can be an amazing source for map data including BLM trails, management area plans, zoning, roads, etc. Utah alone has over 1TB of GIS data available for download ([url]ftp.agrc.utah.gov[/url]). Search online for you State - good stating keywords are "%your_state% shapefile" and "%your_state% ZIP shapefile". Between the 2, you should be able to drill through the fluff to find your state's repository.