Does iOS 8 allow me to share URLs without opening them first? Does iOS 8 allow me to share URLs from eg the built in mail app (or any 3rd party mail apps) via the new sharing extensions, without actually opening the URL first?

I'm particularly interested in sharing URLs to getpocket.com or similar services; their app supports the new sharing features, but the only way I've seen to be able to share a URL is to load it first in eg Safari or Chrome; casual tinkering with an iPhone 6 in the Apple store suggests it won't do this (I still only get the standard "save to reading list" options), but maybe I'm doing something wrong...
Sorry no, you are correct in that the only options for a URL within Mail are to Open, Add to Reading List and Copy the URL.

I tried the third-party email app Mailbox and it doesn't actually recognise a URL and offer any options. If you hold your finger over a URL it just selects part of it and offers to Copy or Define it.

I also tried the Gmail app and it just offers the same three options as Mail.