If you actually need to answer the phone it's tough.
The way I do it is I don't have ICQ on, I don't answer the phone and I use MS Outlook to set my entire schedule for the day.
I schedule everything in there, every little task, even chatting and making lunch and eating. etc etc. I even put in my morning shower. I view my work day as starting when I step out of bed so I put everything in there till the end of work. I actually hate living by such a rigid schedule but it does help me get things done.
It really helps you to see how little time you actually have to get things done and reminds you how focused you need to be in order to get things done.
Sometimes I just don't feel like following such a rigid schedule and I get very little done. Some things done yes but very little. The thing is when I do give in and follow the schedule and get so much done I'm usually happier with myself for achieving so much.
Nice thing about outlook too is you can move the times around for stuff so as long as you know you need to get those things done you can mess with the times and not have to be so rigid.