Can anyone tell me which SSD suits MacBook A1181?

I do question your direction going with a SSD either to replace your current HD or your optical drive (as a second drive) with this system given what you claim your usage will be with it.

If music and vids are your prime usage they need lots of space Vs need for high speed access (HD Vs SSD) if you plan to store them, even for a short time.

Web browsing doesn't benefit with SSD.

The need for fast cold booting Vs being in sleep mode warrants having SSD as well as fast loading of apps. Unless your using the system in class your need for this is limited, granted who doesn't want a fast booting system ;-)

Given the fact your a student on a limited budget I would recommend upgrading the HD with a 1 TB HD Vs 720GB SSD it will be a lot cheaper and offer you the most benefit. Here in the states you can pick one up for less than $100. Swapping out your optical drive for the SSD then limits you as you won't be able to play any CD's or DVD's without a external player.

Standard vids downloaded from iTunes are 720p and the HD versions are 1080p. Your system will have no problem running either in iTunes (720p on internal display).

You will have some issues running MKV files review this to make iTunes run these formats AVI & MKV in iTunes. As your display is limited (can't play 1080p natively) you will need to down size the resolution of the vids so it will work, unless the player you are using does so dynamically.