s/These are all variations on the same thing./These are all the same thing./
Fixed that for you.
The differences between them are close to irrelevant. Though I find the mouse following a little irritating, so the last one is a wee bit better.
But, the things I think are wrong:
Too much. Over overwhelmed.
The Filters interface is horrible. I couldn't find what I was looking for at all. Sliding through the list looks awesome...but it's really time-consuming to use. A dropdown would have been faster, and would be what users expect. A simple textbox with auto-complete might also be a way to go about it.
There are too many types of filters for a front page. Make it keywords by default, and hide the rest on an advanced search page.
Or, simply get rid of "filters" and make search work really nicely. That'd remove a huge amount of the confusing stuff on your page...but maybe filters are worth having, regardless of clutter...you can decide that. But you definitely need to do something about those filters.
The rest of the page might be a bit busy...but it looks pretty nice.
One thing you might consider is making a bunch of language specific versions, e.g.:
perl.siafoo.net
python.siafoo.net
java.siafoo.net
Or siafoo.net/perl, /python, etc.
Most people looking for a snippet of code will need it in their own language. Sure, a lot of developers are happy to learn new techniques in many languages, but if it's a "here's where you go to find the bit of code to do this tiny thing" kind of site, then you probably want it to be obvious how to find the right language. The "Languages" filter obviously already provides the functionality...so maybe a direct link is trivial to add.