Starting a Startup, still in concept and idea phase, How to put what progress/accomplishments on resume?

Great question!
If creating a startup, why would you need a resume?
For now let's assume you're looking for a side job and want to use this as experience...
Focus not in what thresholds you might have accomplished but the route you took to get there. For example, describe your ability to effectively communicate a problem and direct a team to develop and implement a solution. Or the number of sales you have generated for the startup ahead of expectations, web design abilities, etc... Unless is a well known brand no one cares if you simply list: "launched a start up company that did x" what recruiters want to see is the applicable value you bring to their company for your applicable job description...

-Humberto Valle

I'll have to echo Humberto Valle when he asks why you need a resume at all when you are starting a startup. This doesn't really make sense and, from an employers perspective, a red flag that says at best you are temporary, at worst you are distracted. I would take a hard look at what you are doing and decide if you want to start something or work for someone. Then, read Humberto Valle's advice on focusing on the outcomes you've achieved while helping with the startup and move on.

Startups aren't part time IMO.

I think business plans are great if you are building a business with a known and validated business model (like a coffee shop, restaurant, retail store, etc.) But if you are building a startup (a new business model that has not been executed successfully before), The Lean Startup (http://theleanstartup.com) method or the Business Model Generation (http://businessmodelgeneration.com) approach are better. Steve Blank's resource, The Startup Owner's Manual (http://www.stevenblank.com/startup_index_qty.html) also has some great practical steps.

While, I know you are looking at this as a theoretical educational exercise, I would encourage you to consider taking some of the steps laid out in the resources I mentioned that are practical steps towards building a real business. There is no reason you can't do these things while in school, and you might just end up with something that is valuable.

Speaking from the resume evaluation perspective, I would put more weight on a resume of someone that has done some of the actual work of building a business, rather than someone who did a mental exercise / simulation on a business.

For example:
- Did market research on the perceived need for a new product and the possibility of building a list of potential customers for the theoretical product (not that impressive and / or valuable in my opinion - this is the old school Business Plan style approach to entrepreneurship)

vs.

- Developed a new product design and pitched it to potential customers. Built website and internet marketing campaign for the new product that generated a list of 2500 customer names & email addresses who expressed interested in the product. (this is impressive and is an expression of the Lean Startup)

Here is a great article that describes the different approaches you could take and how great entrepreneurs behave: http://www.inc.com/magazine/20110201/how-great-entrepreneurs-think.html

Entrepreneurship is a hands on exercise. Jump in and go for it.

When I hire people, I actively search for people with side projects, either current or past.

I'm not interested in the skills they've obtained from them, I'm just searching for a "self started" or motivated person.

People who start side projects are generally more passionate and have a greater understand of the overall process of the working environment.

Just simply mention that you're motivated by starting things and building them from the ground up, and that you're currently doing that now.