I love Gittip. I don't love the homepage.
When I visit the homepage, I see "Sustainable crowdfunding: inspiring generosity", followed by a call to action input asking me to enter someone's username, and finally three groups of lists of people. None of these things mean anything to me if I'm new to Gittip.
The headline at the top describes your company mission statement, not what the product does. Instead of telling me the abstract of what Gittip is about, it should tell me the benefit of using your product. For instance, "Support your favourite people by automatically donating to them weekly." Skip the generosity, sustainability, and crowdfunding mentions for now. Put them behind the About link, which I might click if I'm interested in learning more about how and why you're doing this (I'm probably not).
The call to action input doesn't help me much. It's asking me to enter someone's name off the top of my head, and it's using a very vague label ("who inspires you?") to do so. I would scrap this approach and instead provide a way to sign up to Gittip with a call to action that ties back in to the headline. So you want to donate to people you like? Step 1: sign up for an account. Step 2: add people from your Twitter, Github, Facebook, etc. Step 3: Look through the list of people (Gittip should use some magic to prioritise the people by likelihood of my wanting to support them, such as looking at how close they are to me on Facebook, or how many followers/stars they have on Github and how many of their projects I've starred) and select up to 3 that I like. Done! Step 4: Decide to give someone something minimal (say, $0.25) per week by entering my credit card details. If I choose not to do that, at leat I made a profile on the site, got familiar with how it works, taught you a bit about who I am and where I came from, and you can maybe email me later and remind me if someone I have in my friends list did something interesting (like published a new project, blog post, insightful tweet, etc)
The list of people at the bottom of the homepage is boring. It's not contextual to the goals of the homepage, which are converting users to understanding Gittip and wanting to join in. Right now you show me static lists of new users, top givers, and top receivers. I don't really care about new users other than as proof that this site isn't dead, so you can reduce their importance right off the bat. Top givers and receivers aren't relevant to me unless you tell me what they're giving or receiving. So I would reformat these lists: andyet gives x per week to a, b, c, and more. ashedryden receives x per week from a, b, c and more. I need to understand that Gittip is about creating a direct personal relationship between people giving money and receiving money. Right now, these lists don't imply any kind of relationship.
I also think you need to revise the name. I know you've decided that "Gittip" is just a new word and shouldn't be understood as a portmanteau of git and tip, but it's a terrible, hard to remember, hard to spell word. "Giddip? So with a D?" "No, with two T's" "The heck does that mean?" "I dunno, it's just some weird word" -- you're missing the opportunity to give the product a memorable, clear, unique name that either represents your product as it stands apart from competition, or is memorable and quirky enough that it just sticks. Patreon got it right: it evokes "patron" but it's slightly different, so you can intuitively guess what it's about and still remember the brand itself.
I recommend reading the book Seductive Interaction Design by Stephen Anderson: http://www.amazon.com/Seductive-Interaction-Design-Effective... - it will help you combine your existing ability to reason about the product with some basic psychology and mental modeling that will allow you to word things in such a way that the benefit is more clearly communicated and you're speaking to the user instead of rambling about the company vision to nobody in particular.
Good luck with Gittip in year 3. I'll be watching - and giving :)