Their line manager makes sure the card goes round for everyone to sign, and spends what cash gets put in the envelope on something they'll appreciate. If anyone missed the internal eMail about this person leaving, now they definitely know.
People get told a few hours ahead (internal eMail) where the short presentation is. Line manager says a few words, hands over card and present. If they've been there quite a while, someone bigger than the line manager may also say some words. Leaver says a few words, everyone claps. Leaver says when they will be in the pub (repeated in leaver's final internal eMail to the department) and leaver buys the first drink for everyone who turns up.
That's how it's been in every company I've left. It's pretty much the UK standard. It's near perfect; everyone knows exactly what's expected and how it will work. No uncertainty, no mistakes, opportunity to chuck in a few pounds or not.