Fish, you mind if I answer some of these, seeing as how your website might take a while?
[li]Is there a sharp and a flat for every note?[/li]
Well, yes and no. Strictly speaking, A,B,C,D,E,F,G can all be flat, natural, or sharp. However, the difference between flat and natural, and between natural and sharp is a half-step. Most of the natural notes are separated by a whole step: A, A#, B. In addition to that, with two adjacent notes (except for the ones I will shortly address), the lower one sharped is the same note as the upper one flatted: A, A#/Bb, B. The exceptions to this are B-C and E-F; each pair is separated by half a step, and so B# is C, and E# F.
[li]What’s the difference between sharps and flats?[/li]
A sharp raises the note to which it is applied a half-step, and a flat lowers it half a step: see my previous answer.
[li]I’ve seen the music staff with the G-Clef, and one with a Bass Clef. Sometimes the former is above the later… what’s the “middle note” between these two staffs… or is there really no difference, and it’s just based on octaves or the instrument being used.[/li]
Technically there are three different clefs; the most common are the treble clef, also known as the G-Clef because in normal position it curls around G, and the bass clef, curling around F (incidentally, that F is just over an octave below the aforementioned G). Usually the treble clef is placed above the bass, because (simplifying somewhat) one ledger line below treble clef is C4, which is one ledger line above the bass clef. Clefs are technically independent of instruments, but in practice because of range many instruments have music written almost exclusively in one clef.
[li]Why do we use treble and bass clef, instead of just putting all of the notes onto the treble clef? I understand that there’s a vaster range per instrument, but I’ve never understood why a bass clarinet can’t just use the treble clef, with the notes transposed accordingly.[/li]
To some extent see my previous answer; as I understand it, though, the issue is often not of a larger range but simply a different one. Shifting octaves withing the same clef isn’t going to help if you’re going to be dealing with a lot of ledger lines anyway. Bass vocalists, for example, can easily range from F below bass clef to C above it; this involves only one ledger line in bass clef, but at least one in treble, with the clef itself shifted two octaves down. There are three different clefs: bass, treble, and tenor/alto; they all center on different notes, and so do instrumental ranges.