Which lens?

[ShutterbugJohan]

I have tentatively narrowed it down to three lenses, the 24-105mm L, the 17-55mm f/2.8 or the 100mm f/2.8 Macro. I Realise the Macro option may seem odd in comparrison, but if i was going to buy either of the other 2 lenses i would also by some extenders to give me some degree of macro capability.

If you shoot in low light fairly frequently, I would recommend buying the Tamron 17-50/2.8 Di-II and the Canon EF 100/2.8 Macro. Together, these two lenses cost about the same as the 24-105L or EF-S 17-55/2.8IS. If you shoot in good lighting conditions, and the kit lens is fine for you, buy the 70-300IS instead of the Tamron 17-50.

The question is, Would the 24-105mm or the 17-55mm prove to be vastly more useful than the 18-55mm kit lens?

Depends. The 24-105 is probably less useful, becuase although you gain some telephoto, you lose some wide-angle (it is easier to crop than to reverse-crop). If you shoot in low light, the EF-S 17-55/2.8IS would be better. Of course, both of these lenses have better IQ than the kit lens.

I think i would appreciate the extra reach of the
24-105 but is it worth the substantial amount of money considering the
lenses i already own?

I would say no, because you lose some wide-angle. If you buy the 100/2.8 Macro, you'll have a wider range than the 24-105 anyway, although not in one lens.

Would i be better off saving my money and going for
the macro lens and perhaps looking at a telephoto in the future?

Probably.

I suggest you go for a dedicated macro lens. I prefer the EF-S 60mm f/2.8, which is more inexpensive, but the 100 is excellent.

I disagree. For macro work with live critters, the longer reach of the 100mm is essential, plus the 100mm has a focus limiter switch so the AF doesn't hunt much when not shooting macro.