Gmail, Gmail, you have won our hearts over the years and a constantly improving feature set has been firmly behind that, but finally, finally, finally, finally you've added two basics that have been lacking for far too long...
In a double announcement Google has revealed Gmail now has drag and drop support for attachments and the ability to insert calendar invitations into emails.
The first couldn't be simpler - and thankfully after so much thinking time is very gracefully done: just drag a file, or files, onto the subject line area and Gmail will switch layout to display a 'Drop files here to add them as attachments' message. Do that and voila! Easy, elegant and long overdue (though currently supported only by Firefox and Chrome browsers for now).
As for calendar invitations, the option to 'Insert: Invitation' has been added alongside 'Attach a file' and once clicked creates a invitation box which looks much like that seen in Google Calendar. If shared calendars are present they can show when fellow recipients are/aren't busy, though once sent the invitations are simply added automatically into all parties' calendars rather than relying on a yes/no reply which is a disappointment.
Both drag & drop and invitations have gone live immediately and it is noticeable Google hasn't messed around by putting them in Labs, they are hardwired into all Gmail and Google Apps accounts.