In our Salesforce.com org we have a custom built Projects Object where we track Project Progress and all sorts of other client related information. It works great. That said another application we use extensively is Evernote. I have to admit I love this little app. It enables me to as my son says to "just remember stuff" and get to it from any device.
When Evernote for Salesforce was first announced at Dreamforce '13 last November I was excited but at the same time a little disappointed by the fact that you could only associate Evernote Notes with Standard objects.
Evernote have now published simple instructions on how to associate Evernotes with any custom object in Salesforce.
Here is a link to the instructions. I warn you it does involve creating a VisualForce Page but hey its always good to learn new things.
Add Evernote Business to Salesforce Custom Objects