I am working on starting my own bootstrapped business also, and am in a similar position as yourself. Start by googling resources about how to bootstrap a startup. $150/week is plenty, although you'll have to save for some bigger purchases.
Firstly, you'll should plan on doing most/all the work yourself. This isn't strictly required, but I find it to be the most fun part of the job. Save the money for advertising, PR, link building, domain registration, company formation, accountants, etc.
Alternately, you can select a product you you want to build, save for a few months, and then just pay someone to do it for you. There was a good interview on Mixergy about exactly this method, where a $2k investment turned into $80k/month. http://mixergy.com/free-apps-interview/ I wouldn't expect to have the same kind of success, but it is something you could pursue.
If you are more interested in sitting back and investing in established companies, a lot of people will try to sell you hot stocks or whatever. Don't listen. In the long run (3-5 years) no one, save a very few people like Warren Buffet, beat the market. Roll some percentage of your money into an S&P index, and international index, and a bond index, then re-balance every year. The closer to retirement you are, the more money should become cash or CD's. The younger, typically the more in stock + international. It's boring, but it's the surest way to have your portfolio grow.
Personally, I prefer the startup route (but I do plenty of investing as well).
Good luck!