I've been playing with an idea for labeling support with Rails form helpers for a while, and I recently polished off the gist of what I'd been aiming at and released it as a plugin.
I bring this up to the list because my recent polishing stint was encouraged after I noticed the label helpers which were recently committed to core. More to the point, I noticed how those helpers are not anywhere near as good as I think such an interface could be.
So, I would like to suggest that the interface which I have provided via this plugin be considered for inclusion in core. If this were taken to by concerned individuals, I would certainly help in providing the appropriate patches.
Please see the README for some examples:
One of the big advantages to this approach is that it is aware of the fact that for most cases the label can be automatically generated based on data already available via the labeled input. Beyond that, this interface provides a flexible way of customizing when your problem veers outside most cases. I also think that a feature like this is natural as an extension of each form helper rather than a standalone helper.