here are some gems I learned about at CalGIS:
1. Go to ArcGIS Online Resources to quickly, easily, and freely add in terrific basemap data and high res imagery to any .mxd. If you are logged in you will have access to a lot more options.
2. Arc 9.3.1 (to be released any day now) will include a "layer packages" feature. So, if you want to send someone your file exactly as you are looking at it, you can right click on the layer and select "save as layer package", and it will zip the .shp + .lyr into a .lpk to share more easily. Also, there will be free access to Microsoft Virtual Earth within your Arc desktop.