In reply to Fredt:
I have the following:
17-40mm L
50mm f1.4 (non L)
100m f2.8 IS L macro
24-105mm IS L
100-400mm IS L (traded in a 70-200 L f4 non-iS)
Bang for buck I would definitely recommend the 50mm f1.4. It's not an L but gives great results and is relatively cheap. The 50mm f1.2 L maes me go weak at the knees but I couldn't justify the cost (or slow focussing!) for normal use. It is only a portrait lens in reality butthe 1.4 is a great option.
I also would defend the "old" 24-105mm. Great lens and is my daily walk around lens.
The 100mm L macro is pin sharp and also an excellent portrait lens if you are able to stand back and/or for candid shots. One of my favourites.
The 17-40 is also a lovely lens, fairly small/light and at a reasonable cost. However, some of the other/newer wides would be well worth considering.