If you do get around to doing some work, don't send it out all at once. Send it out at intervals to give the impression you have been working continuously.
Remember that holding down the Windows key and hitting 'M' minimises all open screens in an emergency should your boss enter the office while you are browsing the web or playing solitare. No idea what is required on a Mac to achieve the same effect.
To avoid being given extra work, appear stressed, this gives the impression you have a lot on and are working at full capacity. Complain a lot about how busy you are, list all tasks, including minor ones and ones that have already been completed to support your complaint.
I spend a lot of time on teleconferences so I have a headset attached to my phone. I often wear this all day even when not on a call to stop people bothering me.
I often turn my laptop on of a evening to browse the web while watching the TV, I always make a point of sending at least one work email ensuring my boss is copied. He has commented on my dedication on working evenings....these helps balance out me coming in at 9:30.
Outlook has a "send at" function for emails. As long as you leave your machine logged in, it'll send the mails at that time.