First of all, what is a "bikeshed" anyway? The term bikeshed comes from watershed, which is a specific area within which water flows to a certain body of water. Planners much more recently created the term "bikeshed" in order to try to capture or visualize the "easily bikeable" area around your home or perhaps workplace. Of course, what's "easily bikeable" is highly subjective. Someone who treats bicycling as a sport is going to include a much larger area in their bikeshed than someone like me who cruises along on a bike like I'm having a Sunday stroll.
As we coast into National Bike Week in the US, a fun activity for many of us might be mapping our bikeshed. If you already bike a lot, you can probably pull out a map and do that right now. If you rarely bike around your city, you can use the opportunity to explore various routes and the limits of your biking comfort and then map your bikeshed.
There are a couple of ways in which this mapping process could be useful, imho. For one, the process can identify areas of the city that really need better bike infrastructure. This could be a very effective way of choosing where to expand or improve bike infrastructure, especially if it is a crowdsourced project involving the creation of a bunch of bikeshed maps.
On a personal level, I think that mapping out your bikeshed can help to show you that there are many subconscious limits, and that you could actually extend some of these in order to further extend your actual bikeshed. We often block out routes or areas of the city simply because we aren't familiar with them. Through a mapping exercise, and especially one connected with greater exploration on your bike, many people will discover that "off-limit areas" are actually quite bikeable and accessible.
So, I encourage you to start mapping your bikeshed today! (Or this weekend, at least.)
If you're interested in learning about some work being done at the University of Maryland where researchers are trying to map out bikesheds in various places using objective measurements, check out: Mapping How Far You Can Bike Without Breaking a Sweat.