Is there like a website where I can download an older version of iTunes (like iTunes 1) for my clamshell iBook ?
As discussed earlier, many of the links for older software are broken on Apple's web site. It appears it is is a low or no-priority thing for them to get fixed because once software is no longer supported it is, well, no longer necessarily supported in any way. In rare cases you can find them on alternative sites, as indicated in the link a_brody posted. With iTunes, however, the most popular non-Apple storage sites removed the files. It is possible Apple told them to stop posting iTunes, as Apple itself specifically does not leave all iTunes versions up in the open (you can find some of them them hidden if you know how, but the truly early versions seem to have disappeared completely). Why they don't we don't know. In other cases it seems Apple isn't concerned or maybe they just never read the forums, or it isn't reported to Apple legal, or maybe system updates have different rules applied to them, or whatever reason, the system update links remain on the non-Apple sites as a valuable resource.
I habitually download versions of various Apple updates I find even if I don't specifically need them at the time, just in case I do want to load it on an old computer or update but not jump as far as Apple will normally require.