The only place where you will be able to find out the name of a film by describing scenes from it will be a search engine such as Google. The complexity of building a reliable database that can identify films based on loose descriptions is too extreme for one to have been created yet.
Your success in finding the film you are looking for will rely quite heavily on your description of it. For instance, remembering a pretty good car chase probably won't help you due to the sheer volume of films with car chases in them, but remembering parts of the script will! Try entering a memorable line from the movie in quotation marks into Google and hitting search as Google uses quotation marks to search for phrases instead of individual words.
There are large numbers of movie scripts posted on the internet, and it is likely the movie you are looking for could come up as a search result if you look for it in this way. At the very least, you should find other people who have posted quotes from movies along with their sources.
Searching for a tagline or an extremely brief description or synopsis could also yield results. As an example, searching for 'epic space battle trilogy' will link you to a page where you can peruse through IGN's top ten space battle sequences, two of which are from Star Wars. It may not be a way to get a direct result, but it's certainly a way to find the answer you are looking for.
A final idea is to ask in online movie forums. Forums on websites like IMDB.com, the Internet Movie Data Base, will have plenty of uses who consider themselves to be film buffs, and if you can describe any amount of the film for which you are searching to a fair level of specificity, it's likely someone there will be able to identify it for you. The IMDB also lists cast members from a vast amount of films, if you can remember an actor from the film, look them up and then check their film credits.
Your success in finding the film you are looking for will rely quite heavily on your description of it. For instance, remembering a pretty good car chase probably won't help you due to the sheer volume of films with car chases in them, but remembering parts of the script will! Try entering a memorable line from the movie in quotation marks into Google and hitting search as Google uses quotation marks to search for phrases instead of individual words.
There are large numbers of movie scripts posted on the internet, and it is likely the movie you are looking for could come up as a search result if you look for it in this way. At the very least, you should find other people who have posted quotes from movies along with their sources.
Searching for a tagline or an extremely brief description or synopsis could also yield results. As an example, searching for 'epic space battle trilogy' will link you to a page where you can peruse through IGN's top ten space battle sequences, two of which are from Star Wars. It may not be a way to get a direct result, but it's certainly a way to find the answer you are looking for.
A final idea is to ask in online movie forums. Forums on websites like IMDB.com, the Internet Movie Data Base, will have plenty of uses who consider themselves to be film buffs, and if you can describe any amount of the film for which you are searching to a fair level of specificity, it's likely someone there will be able to identify it for you. The IMDB also lists cast members from a vast amount of films, if you can remember an actor from the film, look them up and then check their film credits.