Google announced Google App Engine today, and while I haven't used it yet I am on the waiting list and I took a look at their docs. They announced it at CampFire One last night, and its already gotten good reviews.
It appears to be the integrated web development and hosting environment I've been looking for (I don't do a lot of development anymore but I always have a need for doing a little development). To date I have yet to set up a dev/hosting environment; every time I've tried something has gotten in the way relative to usability or functionally working. Hopefully Google App Engine works :)