Chain lightning in 3.5 doesn't really fit the flavour of the AD&D version; if anything it's more like "web lightning".

Inspired by nonsi's Spellfire thread, particularly Spellfire Bolt and Spellfire Serpent (and to an extent Spellfire Storm, in that this spell can wipe out an army).

Greater Chain Lightning
Evocation [Electricity]
Level: Sor/Wiz 8
Components: V, S, F
Casting Time: 1 standard action
Range: Long (400 ft. + 40 ft./level)
Targets: One target/level; see below
Duration: Instantaneous
Saving Throw: Reflex half; Fortitude negates
Spell Resistance: Yes

This spell creates an electrical discharge that begins as a single stroke commencing from your fingertips. Unlike lightning bolt, chain lightning strikes one object or creature initially, then arcs to other targets.

The bolt deals 1d6 points of electricity damage per caster level (maximum 25d6) to one target per caster level (maximum 25). The spell also damages all creatures in a 5-foot line between you and the first target, and between each additional target and the last. The bolt arcs from target to target, determining a new line of effect each time from the most recent target. Creatures in the area of multiple lines created by this spell only take damage once.

Each target can attempt a Reflex saving throw for half damage. You choose targets as you like, but they must all be within the spell's range from you, and no target can be struck more than once. You can choose to affect fewer targets than the maximum.

Focus
A bit of fur; a piece of amber, glass, or a crystal rod; plus one silver pin for each of your caster levels.