Tarsnap is great and secure. Not just any HN user, Colin Percival, security officer for Freebsd and a Putnam fellow. It's a very practical and well priced option.
You'll have lots of fun picking up Clojure. I'd recommend 'Clojure programming' by Chas Emerick... or 'Programming Clojure' by Stuart Halloway.. to get started and then 'The Joy of Clojure' by Fogus. My advice would be to not immediately get bogged down by taking on a large project (like an existing rails app) if you don't already have some experience with functional programming. You'll have a much nicer perspective on the Clojure way of doing things after you work through those books.
Nothing about that posting screams phishing or scam. This is very normal for companies trying to keep a low profile before launch. They've provided enough information that would appeal to a candidate interested in machine learning.
* product details : bringing machine learning to the masses...The first application of our technology is to battle fraud online.
* technical details : Our system uses a combination of supervised classification algorithms, anomaly detection, and good ol'-fashioned feature engineering to ferret out the bad guys, all running on top of open-source tools like Hadoop, HDFS, MongoDB, Vowpal Wabbit, and d3.js.
* funding situation : We're fresh out of this summer's YCombinator batch, raised funding from top angel
* team info : Our team includes two former CTOs, the tech lead of Android voice input, and the tech lead of Google's A/B test analysis framework and IP geolocation teams.
If I wasn't already working on something interesting I'd jump on this.
Github is a neat way to host projects. A link to a repository or a hosted application is infinitely more consumable than a video demo. The Github bootcamp has tons of info: http://help.github.com/, and would be a great place to start. Don't worry too much about your credentials on paper --- put together code samples that demonstrates your ability to work with the languages and frameworks you mention. There are several startups that would love to hire a motivated, resourceful hacker.