It's actually not such a good idea to put only your OS and apps on an SSD. It's easy to notice the benefit (fast boot time and app startup) but how often do you need to reboot or restart your apps (assuming you have enough RAM, which would be a cheaper upgrade than an SSD)?
The temp files and the user profiles are one of the things you benefit most from having on your SSD.
Libraries are a different matter. It depends what you're talking about exactly.
What shouldn't be on your SSD is movies and to a lesser extent other multimedia files, unless perhaps you're actually working with them.
If you keep around stuff like ISOs or service packs, there's usually no point in keeping them on your SSD either.
In many cases you can easily configure default directories and such. But some other directories are hard-coded like some large system directories containing librairies you don't really need to have on your SSD.
If you want to put some non-configurable directories on a different drive, look into this:http://en.wikipedia.org/wiki/NTFS_junction_point
Drives for video editing need to be considered carefully.
Having a dedicated hard drive or array for the files you're working on can be useful, sure. But hard drives noisy, bulky and consume power.
Using an SSD for video editing can be even better. Some SSDs are worse than hard drives and others are better.
But maybe you don't need to do anything outside of the ordinary.
The requirements for video editing tasks vary a lot. You need to figure out how much throughput you need if you want to take an intelligent decision, especially if you haven't bought the SSD you're talking about. If you already have it, you could simply try to work with different drives, see what works best and only buy something new the day you're actually faced with an intractable performance problem. Then you could describe that real-world problem and find a solution.
I doesn't usually make sense to have a drive dedicated to pictures.