Chia can be fun for that, especially in savory applications.
I've found that instead of simple "replacements" often it's better to look at specific ingredients and their characteristics to see if they could fulfill the same function. For example, banana bread: mashed banana essentially acts like egg, so there is no need to really replace the egg (in fact, in baking most things I find that unless it is a recipe with lots of eggs it's just no big deal to leave it out, or use a bit of cornstarch to add some texture).
Nowadays there are enough vegan sites and cookbooks that you probably are better off looking for a specifically vegan recipe than converting a non-vegan one.
Another recent discovery in our kitchen has been the 'chickpea flour scramble' as a substitute for scrambled eggs. Just google that phrase for many recipes out there. The one addition I like to make is the use of Himalayan black salt which is quite sulfury and gives it that more eggy flavor.
“The most important decision we make is whether we believe we live in a friendly or hostile universe.”― Albert Einstein