Q: I want to search for a certain person's slideshows.
A: If you know that person's username or at least one of the their slideshows, you can access his/her public page as follows:
Above the slideshow, you will find the linked username of the creator. When you click on the username, you can see all the public slideshows of this user. For example, username cappy's public page is at http://photopeach.com/user/cappy. Please note that you can see only "public" slideshows.
Also, you may wish to refer to:
Q: How can I follow a certain person's new slideshows?