In your search for a specific chord, you can use a chord finder, or you can be the chord finder. Just keep looking up chords on the computer/online-chord-finding dictionaries, and you will always need the help. On the other hand, if you really learn and master the basic triads ("Triad" refers to a 3-note chord), consisting of 12 majors and 12 minors and 12 diminished, you will have the foundation laid for figuring out any chord you might need.
Piano Chords, along with the piano scales, are the basic building blocks of most piano music. Learning the chords develops your keyboard awareness, and enhances your understanding of the music you read, memorize, compose, or improvise.
Once you have become familiar with the 12 major triads and the 12 minor triads and the 12 diminished triads in root position, you can begin learning how to invert them, voice them differently, spread them out, use them in melodies, and create accompaniment patterns with them. Some pop music, and just about all jazz music, calls for adding extra notes to the basic triads (6ths, 7ths, 9ths, 11ths, 13ths), but you must first know your triads, inside and out. You will also find the triads handy for analyzing piano pieces you might be reading or memorizing. Thus the process of learning how to play the music (and memorize it) becomes much easier than if you had no such knowledge of chords.
Here, you will not find any fancy, technology-aided chord finder (sorry), but a comprehensive list of all the triads (excluding augmented triads, which are rare, but easy to make by simply raising the fifth of a major triad by a half step). You may use the list just to look up certain chords, but I would encourage you to take the time to really learn them all and play them on the piano, regularly. They are as important to the pianist as the alphabet is to the writer/reader.
Once you've learned the chords in these groups, the next step is to play them chromatically: up and down in half-steps. Thus, you will find the same major and minor triads listed in half steps if you go to "Major & Minor Triads".
Once you know these triads in root position and can play them proficiently up and down in half-steps for at least one octave, try playing them around the circle of 4ths. This will not only increase your knowledge and feel for each chord, but will improve your keyboard awareness.
To learn more about developing keyboard awareness, go from "Piano Chords" to "Free Piano Lessons".
For a page devoted exclusively to diminished triads, go to "Diminished Chords".