I was taught a little about SASS mix-ins and a couple other cool tricks, but don't really remember them.
I am not too familiar with HAML or SASS.
What is your level of Sass and Haml knowledge? This can help me set tasks according to Your level of understanding. Also, it might be a chance for us to get to know each other more. If needs be, I might invite someone to be an organiser, I'm no master at these technologies.
I've used SASS/SCSS a little bit in a couple of projects, but I'm by no means an expert. ;)
I've used HAML once or twice in very small ways for very small views. I liked it well enough, but learning a new language (markup or otherwise, even one based off another one) is always a slow process. Gotta use it to learn it!