It would be very helpful to be able to see, at a glance, a list of all billable services (like Linodes, backup addons, etc.) along with their renewal amounts and dates, particularly for accounts that have, like, a dozen servers on all different kinds of billing cycles.

All of my servers are on the same billing cycle. When you add another server, its prorated. It bills you until the end of that month (or if the end is in only a few days, it bills you the remaining time in the month plus 1 more month.) That way all of your servers always are billed on the first of the month.

It would be nice to have a overview of what my next bill will look like.

+1 for this feature. Right now I run 4 linodes which all have different billing times, and I'd really like to be able to see when each one is coming up for renewal.