I handed in my notice at previous employer. As I was going to a competitor I was put on garden leave immediately. The 4 weeks notice was up and I've since started in my new role.
There were a few people that I'm sorry I wasn't able to say goodbye to. The company policy was that announcements on leaving the business were to be made to colleagues when given the say so by line manager. This never happened. The company seem to have a hush hush way of handling departures...the first we used to hear about it was "X has been exited from the business" and then we'd see on LinkedIn they'd gone elsewhere.
There are a handful of people I'd like to say sorry didn't get a chance to say bye, would like to keep in touch professionally etc. Is it appropriate to drop them a line on LinkedIn in? I'm thinking rather that than directly email them at work.
With us, people usually mention it to people they work with - I've been to quite a few leaving dos, and in some case, there are collections and cards (though not in all cases.)
It's definitely appropriate to keep in touch on LinkedIn. In a few cases, I am FB friends with former and current colleagues, but only ones I'd consider going to the pub with, and would consider friends.
You could do as one guy we had leaving today, who send a mail to a rather wide distro list to say it was his last day, and at the end included his contact details for LinkedIn, Facebook, Twitter, 2 personal email accounts... If he sends me a LinkedIn request, I may respond, but I will be ignoring all the rest of them.