I'm 33 weeks and still most of the people I know don't know about it. It's pretty hard to hide now (although according to a woman in a shop today apparently not) so if I meet someone they'll be able to tell but I always found it really awkward to just come out with im pregnant. Time never seemed appropriate so I didn't bother.
Last time I told people when i was 24 weeks. My DD had been asking if there was a baby in my tummy so I thought it was time! I liked keeping it to myself, I didn't want a big announcement and if did hadn't asked, I would have literally kept it under wraps until I couldn't conceal it any longer.
This time round I'll wait until at least after my anomaly scan.
I told work and colleagues at 5 weeks, just because I thought I'd rather them know why I was having appointments and days off etc, my oh wanted to tell the world he was so excited so we pretty much did around 6/7 weeks! I was worried about telling people so early as I didn't want to jinx it but it's entirely up to you!
Haven't done a big announcement just told people as I see them. Currently 19 weeks. However there are pics of me on fb from a hen do this weekend just gone and it's very obvious so i'm sure loads more people now know!
I told my work as soon as I found out (4+4) as due to the nature of my work they needed to make adjustments straight away. We told parents straightaway too because we wanted them to know. Rest of the family/friends, we've told some and will tell the rest as we see them. I'm only 6+1 now and feel like everyone knows! If I hadn't had to tell my work we'd have kept it quiet a bit longer.