When trying to spread the word about Blastoff to build your business, it's important to join lots of different networking sites. Where you can join up with other people to discuss your business opportunity and join in different discussion groups. Spreading the news via Facebook and Twitter or MySpace is fine. However I think you also need to expand out from there. I belong to groups such as Start up Space, Networking Online, SoAct, The Free Marketer Networking site, Entrepreneur Connect, & EnerjizedLife. On each of these sites I have joined other groups and started up my own groups in the hope of building an online presence. I also host blogs on these sites, as well as on posterous & blogger. This all takes time and is a slow process that I hope will open up opportunities for my Blastoff Business. 
I also have placed several free ads regarding Blastoff in different parts of the state. All these things take time and effort. Just like any other business, you have to be willing to put the time in to make it successful.