Are there any limitations to what you can carry or where you can carry within an eruv on Shabbat?
Anything that would be useful for use on shabbos you can carry within an eruv (if you follow the local eruv)
Even within an Eruv, one may not enter non-Shabbat-compatible buildings (e.g. stores) on Shabbat.
Even within an Eruv, one may not engage in non-Shabbat-compatible activities (e.g. gardening) on Shabbat.
Even within an Eruv, one may not handle Muktza items (e.g. a hammer) on Shabbat.
See the link for more details and examples.
You cannot carry things for after shabbos - separate issur of hachana