Here's a schedule of performance times so you can plan your weekend.
The nominations for the most prestigious awards in the UK theatre calendar have been revealed today.
The websites drew complaints that advertised prices were misleading
Helen Mirren and Billie Piper are both up for the Natasha Richardson Award for Best Actress at tonight's Evening Standard Theatre Awards.
Helen, who has already won an Oscar for playing the Queen, competes for her role as the monarch in The Audience.
Billie, shortlisted before in 2007, makes the final five this year for her role in The Effect, as a troubled young woman participating in a clinical drugs trial.
Kristin Scott Thomas, Lesley Manville and Linda Bassett are also up for the gong.
Damien Lewis will host the event at the Savoy Hotel tonight.
Tens of thousands of people have watched some of their all time favourite musicals today for free.
From Matilda to Wicked - 30 West End productions are being showcased in the heart of the capital all weekend. Phil Bayles got a sample of the action.
-It's the largest event of its type in the UK and thousands of people are expected to visit central London to see West End performances for free all weekend.
-Performances are programmed on stage 11am-6pm on Sat and 12pm-6pm on Sun.
-Entry is on a first come, first served basis.
Stars of the West End will gather in Trafalgar Square this weekend for the annual theatre and musical festival West End LIVE – a weekend of free entertainment from London’s topshows and the largest event of its type in the UK.
More than half a million people are expected to gather for live performances from West End favourites like Billy Elliot The Musical, Jersey Boys, Disney’s The Lion King, Mamma Mia!, Matilda The Musical, Les Misérables, The Phantom of the Opera, War Horse and Wicked.
There will also be an exclusive preview of new musical From Here To Eternity on Saturday introduced by the legendary lyricist Sir Tim Rice.
Lucrezia Millarini outlines the runners and riders at this year's Olivier Awards - the most prestigious prizes in British theatre.
The nominations for this year's Olivier Awards have been published today - and leading the field is The Curious Incident Of The Dog In The Night-Time.
The National Theatre production, based on the hit murder mystery novel about a boy with Asperger's syndrome, has been named in eight categories, including Best Actor, New Play, and Director.
The toe-tapping new musical Top Hat follows in second place, with seven nominations, while the West End transfer of Chichester Festival Theatre’s Sweeney Todd is also in close competition with six.
The Olivier Awards are seen as the most prestigious awards in British theatre - and have even been dubbed the "Oscars" of the West End.
The hit Broadway show "The Book of Mormon" opened in London's West End last night.
Stars, including the cast of Downton Abbey and actor Damien Lewis, flocked to the Prince of Wales Theatre.
The no holds barred musical is from the creators of US TV show South Park.
A year after an autistic child had to be treated during the musical Wicked, a scheme has been set up to make it easier for those living with the condition to enjoy the theatre too.
Some shows will now offer what's being called 'relaxed performances'.
Glen Goodman has the story: