According to the Wimbledon website this is number of tickets available to be sold for those queuing:
• Centre Court - Approximately 500 tickets are available each day at the turnstiles EXCEPT for the last four days on Centre Court which are pre-sold.
• No.1 Court - approximately 500 tickets are available each day at the turnstiles.
• No.2 Court - approximately 500 tickets are available each day at the turnstiles only for as many days as a full programme of matches can be maintained.
• Ground - several thousand tickets are available each day at the turnstiles entitling use of the unreserved seating and standing room on Courts No.3-19.
Further info: www.wimbledon.com/tickets
If I hear numbers, I'll try and update this, or others feel free to chip in so people can decide whether or not it's worth heading to SW19.
Certainly last year you'd hear Wimbledon announce about lunchtime that there were so many in the queue that anyone not already in the queue, then don't bother because you weren't going to get into the grounds.
Ground capacity is 38,500. Once that is reached, they operate a one out, one in system.
Monday, June 23 (06.30). according to the BBC Breakfast News there were already 3,500 people in the queue.