Yes.. I believe Intel has discontinued their Slot 1 line of PIII processors. The only ones you'll be able to find these days with 100FSB are the 850 and the 1GHz versions, and those are becoming quite scarce (believe me, I just looked)
More interesting though is the powerleap slot1-socket370 adapter which lets you use the new Celeron 1.2 tualatin core. This is basically the fastest processor a 440BX motherboard can now support.