From Central or Wynyard in the city, any bus with the number between 184 and 190 will go through Collaroy. The express buses (e.g. E87) won't stop at Collaroy, though most limited stops buses (e.g. L90) should, unless they say 'First Stop Narrabeen' (if it says 'First Stop Warringah Mall', this is OK). Ask the driver to be sure.
There's not much to see in Collaroy except the beach. Though it's actually the same beach as the more famous Narrabeen beach (that is, there is no headland in between them), Collaroy is much calmer and has perhaps the smallest waves on the Northern Beaches. For this reason, it's a good place for beginners to learn how to surf, and because of this there are 'surf schools' you can take at Collaroy.
There are two places nearby where you can have excellent views. The first is Long Reef headland, just south of Collaroy, where there is also a spectacularly situated golf course. The second is Collaroy Plateau which rises behind Collaroy to the west and gives a grand view from a lookout point across the Northern Beaches.
There is an Art Deco twin cinema on Pittwater Road, its great big blue facade is a living piece of history that gives the ultimate cinema experience, a real family orientated cinema. The Surf Rock Hotel is big with locals on a Friday night, with live bands and a line out the door.
Long Reef Golf Course offers one of the most scenic (if windy!) courses in Sydney.
Collaroy is home to the iconic retailer Larry Adler Ski & Outdoor. Make sure you drop in and watch out for Santa climbing in the window at Xmas time.
There are a number of beach style cafes and a Chinese, Thai and Indian restaurants on the Main strip along Pittwater Road.
The newly re-invigorated Surf Rock Hotel brings in locals from all along the beaches, especially on Friday nights.
For budget travellers, a popular HI youth hostel is just off Pittwater Road very close to Collaroy's main bus stop and a two-minute walk from the beach. Beds start at $26.