Anto saidIsn't 'Pagan' a really general term?
Do people really believe in this sort of stuff or is it more just for fun?
It's a broad term that generally refers to any number of pre christian European religions. Some people dabble for fun, but for many others it's as significant and lifelong a devotion as any serious "mainstream" religion adherent's. My first boyfriend and his lesbian pals were all Wiccan and had their own circle. They considered themselves Pagans, but also considered those following Druidic, Shamanistic and any number of other systems equally Pagan and equally valid.
Taking off from GS' definition, paganism technically refers to any number of non-Abrahamic belief systems and, as a general term, could refer to everything from animist belief systems, Buddhism, Hinduism, Shinto, etc. In its common parlance in the US and in Europe, typically individuals who identify as pagan are members of reconstructive or syncretic belief systems based on pre-Christian and/or early European religious traditions.
To make things a little harrier, there's a further delineation between neo-pagans and reconstructionist beliefs. An example of the former would be adherents to Wicca and (arguably) neo-druidic groups; the latter would include individuals seeking to re-connect/recreate the religious traditions of early Europe/Levant such as members of Asatru/Theodism or members of Hellenismos.
As far as I've been able to discern the neo-pagan movement arose in two major strands: first during the romantic nationalist movements of the 19th century and, roughly around the same time, with the combined publications of the Theosophical movements and the Golden Dawn. During the first "surge" there was a renewed interest in "folkism" and many individuals took up practicing devotions to the deities of their ancestors - we see this most markedly in Germany with the reemergence of Wotanism and like beliefs and in Britain with neo-Celticism and Druidry.
The second "surge" would add a metaphysical bend to things and resulted in a more "magic(k)" based philosophy. In particular regards, Gerald Gardner created Wicca around the 1930's/'40s and, using the base materials from Margaret Murray's "witch-cult" hypothesis, LeLand's "Aradia", and his charter of initiation from Aleister Crowley, ended up publicly announcing Wicca in the 1950's as "the Worlds Oldest religion".
Myself, like Czarodziej, am an initiate and adherent to the religious tradition of Thelema which grew out of the philosophy of Aleister Crowley. In many ways Thelema/O.T.O. can be said to be the "parent" of the modern neopagan movement, although I personally do not identify it as such with the exception that it is non-Abrahamic in origin. In one way its much more like Buddhism and Taoism in that it can be said to represent a spiritual philosophy and actively draws upon many sources (e.g. yoga, meditation, comparative religious studies, psychology, sciences, etc.) in order to generate a wider range of understanding the human experience. In addition, I'm also ordained clergy in Ecclesia Gnostica Catholica - the Gnostic Catholic Church.