There are many maps shown on this website, mostly showing routes for various tours. These maps were constructed beforehand, with the view in mind of finding a relatively safe way through complicated high traffic areas. They make use of local bike maps, rides graphed on bikely, google satellite and street view, and various blogs and other material from the internet. The best way to make use of these is to put them on your garmin device, then have it guide you as you do the tour. It really makes a remarkable difference. You won't get lost, and will spend a lot less time hunched over maps. We have used this technique to ride through Los Angeles, San Francisco, San Diego, and Seattle. I would say about 90% of this has involved quite pleasant low traffic riding.
Anyway, it is pretty easy to make use of bikely maps on your garmin (edge 605 and 800 are the only models that I know anything about). Open any map that interests you on bikely (i.e. www.bikely.com) - for example, open this link in a separate tab. It will show you how we went from LA airport to Irvine.
Now click on the sharing tab, then download gpx, and save the file that is offered to your computer somewhere. This will be a text file with a bunch of xml in it. This is the information you want to put into your garmin. As an aside, you can also load this file into other mapping software, for example Qlandkarte.
Now connect your garmin with an usb cable to the computer. The garmin will appear, looking like a standard usb key, with folders and the like. Copy the gpx file from your computer to the GARMIN/GPX folder on your edge 605, or the GARMIN/NewFiles folder on your edge 800. If you have a microsd card in the garmin, it will appear as a separate device. Don't use it, use the main Garmin device to store your route.
Disconnect the device from the computer, and start the Garmin. The ride you just saved will turn up in the 'saved rides' option in the 605, and the Courses option in the 800.
Once you get to the ride location, you can tell the Garmin to navigate using your saved ride. To make this work best, you should alter a couple of settings. Set the Garmin so that north is always at the top of the map (otherwise the map will change erratically as you ride, making it impossible to follow). Then -very important- turn off recalculation. Then the Garmin will simply display your ride on the map and show you where you are relative to it. Then it is quite easy to follow. If you don't do this, the Garmin will drop your ride as soon as you stop for coffee, or otherwise get off course, and keep trying to find its own way to your destination. Your map is then useless.
Incidentally, you don't need to buy expensive Garmin maps. Openstreetmap maintains a digital world map, thanks to contributions from everyone everywhere. Creating a world map is kind of an ideal collaborative project. In any case, much of it has been tweaked to make good bike maps. An exhaustive selection of Garmin maps are available from the open street map wiki. If you want to customize your map (for example, if your Garmin won't open your microsd card - or you just don't have a microsd card), use the Lambertus site to get a map that fits into your garmin without the microsd card.
Once you have one of these maps (i.e., you have something with the extension .img that you got from one of these sites), rename it GMAPSUPP.img and put it in the GARMIN folder of your device (if it is small) or of the microsd card if it is bigger.
Finally, once you have done all this, you can draw your own bikely maps. My only word of warning, it is very time consuming.