Lina Inverse, self-styled beautiful sorcery genius. Small, red-haired and with a temper to match, she is one of the most powerful (black) sorceresses around (and she is very clever too) but she prefers to use her power and brains to get herself money and/or food rather than for any altruistic reasons.
Gourry Gabriev. Lina's partner (as of Slayers series 1 episode 1). Tall, blond, superb swordsman with a very special sword (trans: lightsabre) and dumb as dirt. Or is he? :)
Yes. Yes he is. --Vitenka (even when he's being surprisingly smart)
Zelgadis Greywords (or Greywolf, however you like to put it). Turned into a human/golem/demon chimera, he longs to regain his humanity and is searching pretty much ceaselessly for it throughout the series. Sometimes this brings him alongside Lina-tachi for a while. He likes being described as a 'heartless magic-using swordsman' but he's alright really. Very intelligent and a very powerful shaman (natural magic).
Amelia Wil-Tesla Sailoon. Princess of the city-state of Sailoon, some say she was created to take the mickey out of SailorMoon. (Sailoon - get it?). She is young, very enthusiastic and totally committed to justice. She uses white magic and is very clumsy.
Xellos. But I can't tell you about him, because.. that is a secret!
There are a host of minor characters - I really can't be bothered to name them all. [Slayers Universe] has a wonderful listing and also a lot of Slayers lore and backstory. It probably contains spoilers, though. I have tried to keep them out of this.
Finally, one last character (from the movies, pre-series):
Naga, a sorceress who follows Lina around claiming she is Lina's only serious rival. Lina calls her 'goldfish faeces' - as in, she trails after Lina. She eats like Lina, drinks like a fish and is extremely well-endowed, to Lina's disgust and jealousy. She wears very little.
Very funny. Slayers does have a (good) plot but it'd be fair to say that most of the series is humour rather than pertaining to plot. That does not mean it's not worth watching - all three series are extremely funny. Great for relief during exam season.
On other thing - the writer of Slayers has famously said that he did not intend to create a romance. However, there are fans at each other's throats about whether Lina goes better with Gourry or Zelgadis, or whether Amelia and Zelgadis have a chance. There are all kinds of combinations, but if you suggest Lina is better with Zelgadis to the wrong fan, your life is in danger.
Slayers has a huge fanbase and a ginormous background of lore about history, magic and whatever else you please. The [Slayers Universe] is a good place to start. Slayers also has an RPG. I haven't seen the book, but I have seen an advert for it whitch has got me curious. --Steve
The slayers RPG is, I think, RandomAnime? - or at least suffers from all of that lines flaws. In other words, it is very pretty - but contains little or no actual information. A few stats and an CategoryAnime/EpisodeSynopsis is about all. --Vitenka