keeping patentable algorithm free

[jeff at alum.mit.edu]

I have a basic patent question that is possibly license related. I
apologize in advance if this is the wrong forum.

I wrote some software in my free time. I think one of the algorithms
is patentable. It's not earth shattering by any means, but that
hardly seems to be a requirement these days.

Here's the scenario:

1) I don't want to spend a lot of money or do a lot of work.
   (i.e. I don't want to go through the hassle of applying for a 
   patent myself.)

2) I don't care if other people use the algorithm.

3) Somebody, somewhere else may re-invent the algorithm and try to
   patent it, and then perhaps keep me and others from using it. I'm
   afraid of this and don't want it to happen.

Why should I do? Forget about the whole thing? Wait for someone to sue
me? Stick the source on my website and it will automatically become
prior art? Release the source under a free software license (which
one?)  and stick an announcement on freshmeat?  Do I contact some
organization with a name like "Patents in the Public Interest?"

Basically, I want to know how to keep this "invention" free.

Thank you,
Jeff

PS Not that it matters, but the algorithm is the automatic list
sorting routine used at mail-archive.com, which is a web service I
run. Apparently, license-discuss is one of the users of this service.