How do you store all the things which you've learnt and information you want to keep?

Blog about it. That way you'll always have it no matter where you are, and that information gets shared with others.

I use Tiddlywiki to keep all of my development notes together, other than notes or handouts that I might get at a meeting that I want to keep. Those go into a folder for the particular project and I add a reference to them in my Tiddlywiki so that they don't get lost in the shuffle. I tag everything with a limited set of tags (rather than going overboard with the tagging, I have a set of 15 tags that cover the projects and categories I need) so I can get back to them quickly.

Works for me.

Otherwise, I blog about them as needed, use drive indexing for massive searching across lots of stuff, and keep a short daily summary of activities (1 or 2 lines) for better recall.

There are several solutions that I have seen people use successfully:

• blog about it (as others have noted here)
• maintain a Wiki (local or hosted)
• keep it in a plain text file
• use Backpack
• use a hosted office solution (Google docs, Zoho)
• email it to yourself in Gmail (yes, really :) well, makes stuff easily search able)

I personally use a TiddlyWiki (easy to use; very good search) which I carry around in a USB pen drive and which is also checked in to my SVN repository; and a small "notebook" (created from here) which fits neatly in a wallet, to jot down things when I am not near a computer.