My contract states that I must give 4 weeks notice in writing to end my contract. The issue I am facing is one of logistics. My boss works schedule is hectic, he either working from home, liaising with clients or working from the office. I am located at a client site far from his location. What should I do to deliver my resignation letter?
I would give him the courtesy of a telephone call informing him that you are handing your letter of resignation in and then ask him if he would like a hard copy or via email. If he would like a hard copy, simply ask him where he would like it sent.
Most companies will consider the clock to be starting from when you have this discussion (and ensure you date your letter with the same date)
You can always put a read receipt on the email as a substitute to the delivery receipt on the snail mail
Mike's answer is already a very good one: call first and ask the manager how he would like you to proceed.
Depending on your place of work and your relationship with both your manager and your current employer, you may want to cover all bases to ensure that your resignation really arrives and to be able to prove it. Email is often acceptable (it is "in writing"), but you may want to go the old-fashioned way of sending a snail mail letter. An email can always end up in a spam folder - or be claimed to have ended up there. If you want to be extra safe, you can send the letter by registered mail, so you have proof your manager or at least his assistant received the letter at a given date.
This may be over-thinking the issue. Nevertheless, managers have been known "not to receive" a resignation. You don't want something like this to delay your starting at your new place of employment.