Perhaps with the recent announcement about the integration of CircuitLabs into Electronics SX, now's a good time to reopen the debate around linking to an online LaTeX compiler?
(Original topic here: Link to online LaTeX compiler )
I'm one of the developers of writeLaTeX, and we'd be happy to discuss the possibilities for this with the SX devs - the original answer by Stefan in the link above generated a fair amount of upvotes. We could always enable the link for an evaluation period and let the community vote on whether to keep it?
(PS: For an example of such links in operation on a forum, see the LaTeX-Community.org announcement when it was integrated there in January, or the TeXample.net site which has similar functionality for the examples there)