The Alfa Romeo Owners club (AROC UK - Official Alfa Owners club) runs Spring Alfa Day and National Alfa Day every year. This has been going for many many years now so not really that new. I have been along to a few over the years myself, but did not attend this one as too far to travel.
They switch venues every year to try and get a spread of attendees from north/south/east/west. Last year Spring Alfa day was at Duxford IWM just down the road from me.
This years NAD is at Chatsworth house in the Peak District on 10th July. A good day out if you are in the area. Non-Alfas are allowed but won't get special parking. I will be there in either a GTV, 155 V6, or 75 V6, not 100% sure yet!!