The issue of how exactly the establishment clause of the constitution is logically implemented is a debate which never seems to take a break. Recently on the American Atheists blog there was a post concerning a judicial ruling that a library would have to allow a christian group to use a conference room to meet for religious service - a room which existed to provide the public with a place to gather free of charge. The library had a pre-existing rule that none of the facilities were open to religious services.
What I find interesting is the debate which followed - a debate among atheists - as to whether or not this was a fair ruling. At one point the issue of freedom of speech came up, but I honestly have no idea how you could turn this into a freedom of speech issue unless you were specifically trying to complicate things. However, in regard to separation and the establishment clause - this is a great issue for debate.
In defense of the decision:
The library rooms are publicly funded and as such are supposed to be open to the entirety of the public. Religious groups comprise part of the public and so should be able to use the rooms just like anyone else. To keep them from being able to use these rooms is actually a kind of discrimination and is inappropriate in regard to publicly available resources.
Because the library is a publicly funded institution over which the government has direct control, the allowance of any religious group to use the public rooms is a violation of the establishment clause because by allowing religions to use public facilities as places of worship, the government is funding these religions by proxy. The establishment clause exists to maintain a clear an distinct separation of church and state, so allowing religious groups to use state funded spaces is a clear violation of that separation.
I honestly feel somewhere in the middle between these two arguments and I'd like to get other people's opinions on the subject. The interpretation of the establishment clause is constantly being debated between theists and non theists and the propensity for non-theists to claim that theists are trying to purposefully interpret the clause to fit their god-agenda is common. However, this is not the first time I've witnessed atheists arguing among themselves regarding the scope and depth of what church and state separation really means which seems to lend weight to the theist argument that the establishment clause is more widely interpretable than non-theists claim it to be.