So I'm looking for a tool, presumably a webapp, that could track the dates of next bill, domain and certification expiration, and such, for many websites.<p>This can be done in a spreadsheet, of course, but is there something shinier for the purpose? Of course you'd need to add the details yourself, but then you'd get a complete view of the upcoming events easily.<p>This doesn't even have to have anything to do with websites - could be just a general app for the same purpose. I can add the cert expiry dates, the app doesn't have to look them for me.
How about Google Calendar or similar? When I freelanced I used a combination of Google Calendar for domain and cert expiration/renewal dates and used Quickbooks to remind me when those dates were as well for billing purposes. I had a separate calendar within my calendar just for these dates and would have Google email me with what was due that day and week. You could even tie Quickbooks in to automatically invoice your customers on said date to take the hassle out for you.