Evernote is an excellent tool for not just taking notes, but recording just about anything, including images and audio. I use it for lots of stuff, from jotting down ideas to writing out blog posts and business plans.
You can use it on both your computer and your mobile device, and it syncs your information across the devices. You can also access your information via the web. I really like using the different notebooks to categorize my ever-growing number of notes, and it’s easy to search my entire Evernote for anything I need.
The same company also has a nice screen capture tool for the mac called Skitch. You can use it along with Evernote to annotate your screen grabs and put simple graphics and callouts on them.
I highly recommend it for capturing your daily ideas. You can even do something like sketch on a real sketchbook, take a photo of it, and have it automatically be added to your Evernote account. You can tag notes and share them on social media right from the app.
And best of all, it’s free… you can get it on the app store of whatever device you want to use it on.