We've put an adapted version of the advanced search form in the main navigation menu of our site so that this functionality is accessible on every page. Users can select amongst various options including size, colour, price, brand, etc.. We call this function "Quick Find." The standard advanced search page and function is still accessible from the usual place.
Some products in the cart have been grouped together as parent and child products. This is used mainly to list different colour variations of products - e.g. the parent product is black, but it also comes in white, blue and red so these extra colour options are defined as children of the parent black product. This functionality is required so that stock levels can be traced in the back end and so that different product pictures can be used on the front end. Another reason is that each product (parent and child) comes in many different sizes.
These search, colour variation and size functions need better integration. Currently Quick Find correctly returns very good results, however there's a problem with child products not showing up in the search results if the parent product doesn't match in all other respects. For example, if a user searches for a small white shirt, even if that child product is in stock, if the (parent) black shirt doesn't have any small sized stock then it somehow cancels out the child product from the search results.
I'd also be interested to hear any ideas about making the form (see attached screen shot) look more modern - perhaps some nice CSS and AJAX/jQuery effects?