Depends on a lot of things really - Split or splitterless; Repeated; Switched....?
Guess you're referring to cable connected equipment & not fibre-optic? Basically it's:
Gigabit Ethernet (over copper), 1000baseT
Length: 100 Meters
Cable: UTP (Cat5 and up ONLY)
Fast Ethernet, 100BaseTX
Length: 100 Meters
Cable: UTP (Cat5 and up ONLY)
Twisted Pair Ethernet, 10BaseT
Length: 100 Meters
Cable: UTP (Cat 3 and up)
Thin Ethernet, 10Base2
Length: 185 Meters
Cable: RG-58 type coax
Thick Ethernet, 10Base5
Length: 500 Meters
Cable: RG-58 type coax
But these are only really guidlines! The better the equipment - The better quality of the signal over longer distances.