Here are three tools that have proven to be incredibly valuable in making my GTD+EN personal workflow run smoothly.
1. Evernote Web Clipper for Google Chrome. I use Chrome both at home and at work. Whenever I see something that needs to be reviewed/read later or something that I want to reference later, I just grab the web clipper and it sends the information straight into my inbox for processing. The proved particularly helpful when we planned our last vacation. I just put the maps, contact info, operating times, and ticket prices of the places we wanted to visit right into EN.
2. iPhone Evernote app. I am convinced that this system would not work without the iPhone app. It is the key to getting stuff out of my head and into the EN inbox. I put in items when I'm working out, sitting on the bus, in a meeting, and I have to admit that occasionally in church. Getting a note typed in is both fast and easy. I don't process items on the phone because it is too clunky, but I do use it to input notes and view my saved searches to remind me what to do next. I always process at a desk computer. I have also tried to process on the iPad, but it isn't much better than the iPhone. The reason that that I process on the computer is to sure the next action is clearly defined and all the tags for that note are in place. This is easier to do with a keyboard and a mouse.
3. Evernote e-mail address. At first I didn't see much value in this, now I'm not sure how it would work without it. I put that e-mail in my contacts list as "Evernote". Then, when I have an e-mail that needs action (either in my work or Gmail accounts), I simply send it to Evernote inbox for processing with all of the other "stuff" out of my head. After it is sent, then I file the e-mail into a folder in Outlook. That way, my inbox is almost always at zero. At first I had a bit of trouble with this system, because I would have to go find the e-mail to respond to after I finished the action required on that e-mail. However, with the search capabilities in Outlook and Gmail, this is not a problem. I can find e-mails in folders just as quickly as I used to try and find them in an inbox with all the other junk e-mails. Keep in mind, the entire e-mail is in Evernote. You know what the subject line is, just copy out of EN and paste it into the outlook search and the e-mail pops right up.
I would be interested in hearing about what tools you use to make the system work for you.