Doctor Who: How The Ninth Doctor Became Smaller on the Inside
Except when you're talking about the Ninth Doctor.
He has 13 television episodes, four comic stories from Doctor Who Magazine, an annual, and six novels. You can literally wrap up everything ever done by Eccleston's Doctor for less than $200, and it's only that high because you'll probably have to drop $50 or more on the comic collection because Panini Comics apparently hates money and keeps letting trades go out of print.
There are no audio stories. Big Finish isn't allowed to mess with anything after 2005. More importantly, there aren't even any gaps to have those stories anyway.
We can infer that there are a few tales that occur between the regeneration of the War Doctor and "Rose", but there can't be all that many because the further you put Nine from the events of the Time War the less we buy how it's left him a shell-shocked survivor. There's a compelling fan theory that when the Tardis takes off in "Rose" and then almost immediately returns to tell Rose that it's a time machine that there may actually years worth of lonely wandering in what feels like seconds to Mickey and Rose. If that's true, there maybe some hope for the Ninth Doctor to fly again.
I doubt it, though. Even though Ten and Eleven are technically in the same boat as Nine in that they are as limited in the expanded universe currently, they have two things going for them. The first is sheer time. Both David Tennant and Matt Smith enjoyed three full seasons each, with the former also getting a nice big chunk of time at the end that leaves plenty of leeway for, well, anything. In that time, there are a lot more comics and novels, and even a series of audio dramas produced by the BBC. You can wander pretty far along the edges of Ten and Eleven without running out of adventures.
The second is more painfully obvious. I don't think that any fan has any fear that we've definitely seen the last of Ten and Eleven. The tenth anniversary of the relaunch series is next March, and if Moffat and his team aren't quietly planning something then I'll eat my fez. Even aside from a television outing, Smith and Tennant have such deep, undying loves for the franchise that it's inconceivable that they're fully done with Doctor Who. What form their future contributions will take, whether it's an expansion of the Big Finish license to include them or perhaps animated specials, I don't know. What I do know is that they feel the weight of the role too heavily to ever not be The Doctor on occasion.
Nine... not so much. He, and he alone, has signed off on infinity as far as I can tell. He's still one of my very favorites, but he's become smaller than The Doctor should ever be.