Here are some other very useful online resources that you can look at while writing your own lab reports:

Physics

This is a PDF document which not only explains the rationale behind various components of a typical lab report, but it also gives you a fully annotated sample report on Hooke's Law with detailed comments explaining the pros and cons of a particular student's report.
PDF Document

Biology / Chemistry

Here is a discussion forum in which there is a detailed format required for writing a comprehensive Biology Lab Report, followed by an insightful discussion between other DP students.
Online Lab Forum

General

This is a rather old write up (from 2002), but it still gives you a good breakdown of how and why lab reports require certain elements.
Old but gold

Click here to find out how you can improve your Lab Report today!