If you haven't been at the V&A Museum in London, you GOT to go. The costume collection over there is totally insane, it's one of the most beautiful I have ever seen. Plus, they always showcase some pieces of the collection in the Costume and Textile hall. You won't be deceived!
Oh, they do have some of the Worth's dresses over there, what a luck!
If you can't physically be there, no problem, they had the brilliant idea of having the entire collection on the museum's website so you can have a look. When I need some infos or inspirations for a new project, that's one of the first website I research, along with the MET's Costume Institute, the McCord Museum, the Kyoto's Costume Institute, the LACMA and the Museum of Fashion.