What other vegetables can be used in cake/muffin baking? Vegetables have been commonly used in baking cakes and muffins. A common one is carrots to make one of my fave - carrot cake. Recently I also found out about adding zucchinis (or courgettes) to brownies and cakes. I also found some recipes advising using beetroot in chocolate cakes. 

I am wondering what other vegetables can be used in baking? Is there anything I should watch out for? Does a certain vegetable pair well with another ingredient?
Ah, you missed the obvious: pumpkin!

This is biologically a fruit, actually, as is the zucchini.
Pumpkin loves same spices as carrot. Maybe even rum or butterscotch too.

Now, beetroot is a veg and colors cakes delectably; perhaps why it was originally added when going stingy on the cocoa.

How about parsnip next? Sweet and nutty, I think pistachios would complement it well in a recipe borrowed from zucchini bread.

more veg here:
http://www.deliciousmagazine.co.uk/articles/how-to-make-cakes-from-vegetables

p.s. if you haven't guessed Rabarber is rhubarb