First off, I have to say, I love the term "unleashed flash". It sounds way cooler than off-camera.
As to which flash, you have to make a decision of whether or not you want to use eTTL (automatic flash) and High Speed sync (HSS). Most people new to flash are going to want eTTL, if for nothing else, to ease the learning curve. It's nice to have at least one flash that can do eTTL and HSS for on-camera use.
But you mention off-camera and portraits. I never use eTTL for portraits, always manual. And I use manual most the time my flashes are unleashed
If my flash is off camera it's stationary, so I probably have a good idea where my subject will be, thus I like the predictability and reliability of manual flash. I also don't have much use for HSS in what I shoot. Actually, I don't like the power decrease, so I make a point to shoot within my sync speed. But other people have different uses and need HSS, and others like to shoot portraiture with eTTL. It's a personal choice, neither is wrong, but if you want eTTL it gets more expensive.
If you want eTTL just get the Canon 430exII. It's a great eTTL flash for a reasonable price. The nominal difference between generic and namebrand flash with eTTL isn't big enough for me to go generic.
If you're ok with manual flash the Yongnuo 560 III is by far the best value there is at $75. It has built in radio triggers to work with RF-602 and RF-603 systems. It's well built, has a good sized LCD screen, and most the functions/features of Canon. But it's manual and can't do High Speed Sync.
Oh, and I highly, highly recommend going to Strobist and reading. Just about all the info you need on flash photography.http://strobist.blogspot.com/2006/03/lighting-101.html