That is a very good question. I also frequently have the feeling that there is no parallel to "lab notebooks" in the field of bioinformatics. Namely, the linear/chronological property of lab notebooks is something that can be difficult to trace in bioinformatics.
There are of course, version control systems such as git, svn or cvs which are mainly used to keep track of modifications in code-producing work, but can also be used to control the versions of a paper or more. I don't know of anyone using this to trace bigger projects, though.
So for all of my projects, I usually have a README file at the root of the project which states the goals and the main steps for the project. Then, I usually prepare a .bash script where I record all the steps as I develop the project. This script is heavily commented and some results might also be recorded here for further reference. I never run this script as such, but it contains all the steps and parameters I used for reproducibility purposes. However, the chronology of events is lost here, so I do not know exactly when I decided to add 'option x' to a program call.
When a project gets bigger, things get more complicated, and I don't have a very defined system to keep track of the chronology.
So I use:
- version control for code and articles
- README file to keep track of main project objectives
- heavily commented .bash scripts to record analyses steps