Most Wiccans believe in reincarnation. Our souls come back lifetime after lifetime, to learn new lessons and to grow as individuals. Between lives, our souls reside in the Summerlands. It's neither heaven nor hell, but a place for our souls to rest and reflect on the experiences of completed lives. You may be reunited with loved ones as well.
People who are unfamiliar with Wicca tend to see the lack of heaven or hell as meaning we live our lives without responsibility. They may not consider themselves doomed to suffer for an eternity in a Christian hell, but they certainly believe that there are consequences to there actions. Those who do 'evil' deeds, will find their punishment in another lifetime. Karma follows a soul from life to life. There fates are not determined by any one single action, but rather by the overall accumulation of actions throughout our lives.
Since many Wiccans are influenced by the pantheons they work with, their views of the afterlife may come from the culture they work with. In other words, if you are Wiccan but work with Norse Deities, you may feel more drawn to the idea of Asgard rather than the Summerlands, even though you are not truly following an Asatru path.
Asatru / Norse
The realm of the Gods is called Asgard, and worthy souls go there after death. There are many great halls in Asgard, for the many Gods and Goddesses. The greatest of these halls is Valhalla, where fallen warriors go after death. Those who did not live a life of glory would go to the underworld Niflheim, ruled over by the Goddess Hel. Niflheim is a dull and cold place, where you would be separated from your kin. Reincarnation does exist, but not all souls are reborn, and it's typically found within a family line, reflecting the importance of family and ancestors.
Kemetic / Egyptian
After death, a soul would have to journey to the Hall of Judgement. There, the heart is weighed on a scale against the feather of Ma'at (truth and justice), by the God Anubis. If you lived a sinful life, the heart would be heavy, that soul could not enter paradise and would be devoured by the monster Ammut. The ancient Egyptians believed that the physical body was needed in the afterlife, which is why such elaborate means were taken to preserve the body.
Hellenismos / Greek
The dead would be buried with coins, to pay the ferryman to cross the river Styx and enter the underworld. Once there, worthy souls would enter the Elysian Fields (paradise). Unworthy souls were sent to Tartarus for punishment. But even then, a soul could earn redemption and rise to paradise. There was also a region of limbo, called Asphodel for the souls neither good enough for the Elysian Fields or bad enough for Tartarus. The judges at the gates of Hades would decide the fate of your soul, or whether you would be reincarnated into another life.