Caches along a route is relatively easy. First thing you need is a list of the coordinates of waypoints along your route. If you are travelling the highway, just use enough points to approximate the shape of the road. In GSAK, do Search, Filter, Arc/Poly and enter these coordinates, one per line, in the dialog box. So if I created a 4-point route from Wells to Biddeford along I-95, I would have:
43.32324,-70.60858Leave "Filter Type" set to Arc/Line. In the "Distance in Miles" box, input how far away from the road you want to search. I had to put 4 miles before I got any results in my search. Click "Go" to perform the search and narrow the list of caches to the ones near the route.
I believe you can have several routes by saving your filters. So you could have a route for a trip north to your camp or a trip south to visit relatives. I have not played with the Polygon and Point types, but I imagine they work in a similar fashion.
Note that when I use USAPhotoMaps to create my route, the coordinates are output in UTM format. To convert them to Lat/Lon, I modified an Excel spreadsheet I found online. If you are mapping your route in a different program, it may be able to give you Lat/Lon without the extra hassle.