What command lists everything in a package?

Hi,
   Two easy questions I'm sure.

1) As an example if I use the code

require(zoo)

then once it's loaded is there a command that lists everything that
zoo provides so that I can study the package?

   Certainly help(zoo) gives me some clues about what zoo does but I'd
like a list. Maybe there's a way to query something but in Rgui under
Win Vista ls() returns nothing after zoo is loaded.

2) Related to the above, how do I tell what packages are currently
loaded at any given time so that I don't waste time loading things
that are already loaded? search() tells me what's available, but
what's loaded? The best I can find so far goes like this:

> a<-.packages(all.available = FALSE)
> a
[1] "zoo"       "stats"     "graphics"  "grDevices" "utils"     "datasets"
[7] "methods"   "base"
>

Maybe that's as good as it gets in code and if I want better then I
write a function?

Thanks,
Mark