Nightlife

Unless you are staying in one of the main cities along the coastline there isn't much in the way of nightclubs on offer. Each village has it's own trattorias and cafes which may stay open late until 1am in the summer. Alternatively you can gather a few mates and head down to the beaches with a guitar, a few bottles to share and party under the stars.
Wildlife areas
Blue Marlin Café (Vernazza) Via Roma 43
Mar Mar café (Riomaggiore) Via Colombo 234d

Free Stuff

Eating your dinner down by the bay and watch the sunset over the med. Climbing the hills to view the vineyards and coastal views, provided you have enough energy to get to the top. Floating in the blue waters watching the odd bird fly by or topping up the tan on the rocks. Or take a leap of faith with the boys in Riomaggiore as they cliff dive into the deep. Magic.

Other Stuff

Apart from the walking and sights there are a few activities to try out while you are here.
Bike rental from the National Park Office in Riomaggiore.
Diving gear to visit the stunning underwater marinelife, there are specific dives and maps available; canoes and kayaks can be rented from Cooperative Sub 5 Terre, Via San Giacomo (Rio) or
Mar Mar (Rio) also hire 2 person kayaks between April and September by the hour and day.
Fishing - asking around you may find some locals willing to take you out for a spot of fishing for the day
Bird watching of the feathered kind can be done from the Torre Guardiola, a nature observation centre and botanical trail on Riomaggiore's Fossola Beach.