How do you guys keep track of everything from star maps to planetary government?

Notes, lots and lots of notes. Buy yourself a notebook where you write all your names and such down.

As a bonus can you keep some pages as well for those ideas that hit you when you least await it.

Essentially, I tell my players to take notes. And put them where we can all see. I use those notes a lot as well.

One of my RT groups use a wiki: http://profitsdemand.wikidot.com/

Laptop, around fifteen meg of text files, and player rewards for keeping the campaign elements up to date on Obsidian Portal. One thing I found rather helpful is a brainstorming tool like Mindmap or https://bubbl.us . Lets you jot everything out, add reminders as needed. Means you don't have to hold the whole campaign in your head at once.

I like wikis, too - especially because everyone in the group can work on it at any time, adding stuff from their characters or uploading houserule suggestions. The perfect place for brainstorming and up-to-date information exchange.

The downside is that it's all digital, but you can read up on the stuff you think you need just before the session. Some groups also keep a laptop at the desk (my d20 Star Wars GM did this, even keeping MP3 files from the OST ready and playing them in low volume to accompany a lengthy narration/introduction or combat sequences).

I'm somewhat split in that I am so oldschool that I'd actually prefer keeping digital stuff away from the table, but on the other hand I also see a ton of useful features in such approaches.

My gaming friends are strewn all over europe, so being digital is kinda a must have. We use roll20 for our battlemaps and dice rolling, but if we'd be playing on a proper table, we'd probably ditch that too.

But, for out of game organisation, a wiki/forum/notttaking tool is a must (r20 is great for that) and we use skype for coordination and scheduling. Every new game gets its own skype text conference.

I also recommend Obsidian Portal. We used to try Google Docs, but having a site that's dedicated to actual campaign tracking is super helpful.