Depends on what you are trying to do.
I often spend an amount of time working through scenarios with my sales reps on a custom project putting together a mind map of what they need to deliver for the customer, basically I force them to go through the seven stages of Initiation, Definition, Design, Build, Test, Deploy and finally Close. Under each of these stages I outline the major activities required for the custom project they need to deliver to satisfy the customer's requirements, I then spend some time cleaning this up using iThouthtsX which is a mind mapping tool which has the nice feature of being able to draw this in a simple picture and produce output in a number of formats including PDF, PNG, Word, Excel, Powerpoint which I use to get everyone to agree on the concepts and rough plan.
When everyone agrees that this is what we are going to do then I take my iThoughtsX mind map and export this into a MS Project XML file which I import directly into Merlin and use this to produce the master schedule. Of course this is only part of the suite of tools a project manager needs, this and the Office suite to produce documents/plans/reports/logs will go a long way.
I might just add that I use iThoughtsX for a whole range of purposes to document processes during the project, brainstorming sessions, define and finalise requirements, record meetings as it allows me to group thoughts and produce output that can be shared, etc. I also used to overlook this process as part of working with a group and organise ideas but gradually found it a valuable step to getting things done for me. Your mileage may vary.