To expand out on game prep, some I use or would like to see:
City generators that give me some notable inhabitants, how much money they likely have to buy things, types of services offered, random color bits to throw in, including multiple districts. High level map (with only major points listed) also good.
"Interesting" treasure - description of art & jewelry, one line summary of books (or at least interesting titles) that I can influence categories (cult, arcane, ancient, etc.)
Monster stat block generators so I can have everything in one place without reentering.
Character generator I'm focused on the rules - but I want them to have all the rules. Missing a new supplement for months means I likely wouldn't use it. And also work with common types of house rules.
Oh, and a wishlist other: Campaign logging integrator
Some simple entry where players can put in recaps, comments about NPCs or anything. And it auto-tags and combines. So if I write a recap and it includes an NPC, info about that is also in the NPC write-up.
NPCs need to be able to go by different names, in case they just have a last name or a campaign nickname like "bald bully guy". Including going back and consolidating if we find out that "evil mastermind dude" and "Crown Price Lotar" are the same person at a later point.
Really wishlist is looking for occurances of non-dictionary words and offering them up (by frequency) as potential new topics/pages. That would auto-populate with the info already written about them if selected.
Easy for two different people to email in recaps without having seen each other's and they both get tagged for the same page since it's the same session.