Since you are targeting a specific niche of people that want to learn internet related technologies, then I would use a PPC program like AdWords to reach your target market.
I would start off slow and start testing to see which keywords convert the best for your site. If you not sure how to run a PPC compaign then I would suggest that you use some of that $500 to buy a good book or program that will teach you, otherwise you can blow through $500 in no time without getting any conversions (don't ask me how I know
