In reply to littleduck:
Nothing bolted on Kef as far as I know. Nothing much near Lassi, the limestone is more akin to chalk. I lived on neighbouring Ithaka for 6 years and climbed about routes there, all trad and loads of DWS/bouldering. The NW coast of Kefalonia has stretches of very impressive limestone cliffs. I've climbed routes near Atheras on the N tip of the Lixouri Peninsula and also on the W coast of Erissos Peninsula, but you need a boat or kayak to access most of them. Climbed a couple of routes on the outcrops in the woods above Sami., including an E3 on the obvious pinnacle. These can be reached via the well-marked path up to the Acropolis above the town.
Best bet for a first visit if time is short are the boulder fields about 5kms out of Sami on the road to Poros. They are easily visible on your left near the village of Grizata and about 1km before an isolated petrol station. They are very extensive and I visited them on many occasions. Might be worth taking a rope and a rack as some of the formations are 15/20m high. Very easily accessible and well worth discovering. DWS N of Fiscardo via the coastal footpath near Dafnoudi Beach. Also excellent DWS on the seacliffs to the W of the old German gun emplacements near Antipata above Fiscardo. Careful how you go in the forest though, there's still a load of WW2 ordinance scattered around!
I do have descriptions of routes climbed on Ithaka, but you really need to stay at least a day or two on the island. My advice would be to go lightweight on a first visit and maybe search out the DWS potential or spend some time exploring the Grizata boulder field, near Sami. Masses to go at there. Also spotted a line or three in the Poros Gorge!