you sound just like me!! They usually call me the "Bag Lady" at work because I always have my handbag/purse as well as a pretty good size tote that I carry a lot of the same things you mentioned (umbrella, a change of shoes, a book/few mags, an emergency kit from the office, etc)
I usually buy something inexpensive as it gets used and abused pretty heavily - I also like to change them out every 6 mos or so (depending on its current condition).
For a while, I was using the "My Bag Cares" tote bag (http://www.mybagcares.com/). it's large but lightweight and can fit on the shoulder. They also plant a tree in your name for every bag you buy! So not only is it an affordable, practical bag, you're doing something good when you buy one!!
I like to use something that's (1) a good size, (2) lightweight, and (3) inexpensive, since I use them pretty heavily and I don't have to worry about ruining it - if it starts to get worn out or I tire of the way it looks, I just simply replace it with another one!
Thank you for everyone's great recs. Vesna, thanks for the pics of your bags. I love love love the pink and mauve YSL, its stunning, I love it, but may be out of my price range. The colours are gorgeous and is just what I am looking for.
iluvmybags - yes we sound alike. I liked the choices you recommended, especially the Marc Jacobs canvas tote as that is a good size for me plus its affordable. I am definitely a bag lady as to add to my main handbag, I also carry a gym bag - so all in all I usually carry around 3 bags a day