Phreaking was still alive and well a couple of years ago in the UK, and I expect it to be still around today.
Basically the main things phreaks got up to were: hacking voice mail boxes, teleconference systems, and PBXes.
To find such goodies, you had to dial, usually manually, hundreds upon hundreds of freephone numbers. (Wardialing)
Voicemail boxes where the easiest to get into, as often the PIN was the same as the box number, or something like 1234, 1111.... Generally phreaks looked out for boxes that were no longer being used, and took them over, setting up a funky little underground communications system for themselves.
Within a voicemail system it was often possible to get at the underlying features of the PBX. This could sometimes allow calls to be made through the system. Freephone call in, international call out; you see the appeal now?
Finally the other favorite toy of pheakers would be the teleconference system. This again could be automated, perhaps protected by a PIN. In some cases on dialing a number you were automatically dropped in the system, greeted to the sound of business people in a meeting. These systems were popular out of business hours for phreaks to have party calls.