Wujen summon Elemental Spirits, which are like elemental nature spirits. They are summoned as a result of a natural element with no complex ritual and no cost but cannot leave their domain, their domain being anywhere within sight of their "birth element" or forcex10 meters beyond. So, if you're inside a roaring house-fire (or in direct view of one), you can summon a salamander. Even a hot summer day, with heat rising from the sunny ground can you call a salamander. Anywhere in view of natural earth can you call a Gnome. A stiff natural breeze, allows you to call a Sylphid and natural water or ice, you can call an Undine. Near plants or trees, you can summon Manitous.
These spirits powers are like a combination of elemental and nature spirit, with domain based powers and elemental projection powers. A salamander for example, can engulf in flame, do extra damage when engaged in melee combat, shoot flames like a fire elemental but can also Guard from accidents within it's environment (ie, protect against fire). Salamanders also have the invaluable ability of Magical Guard, which allows them to give spell defense to a number of people or objects equal to its force, including other spirit powers. They can also telekinetically move objects.
Basic Spirits of the Elements can only be summoned on a one-for-one basis. So you cannot have two summoned at once, otherwise the other disappears as you are considered to have left it's domain. However, greater-form spirits behave more like elementals insofar as they can leave their domain, meaning you can summon a number of them equal to your charisma and have them "on-call" Greater forms also get the marvelously scary STORM power and the cleansing ability, perfect for getting rid of that nasty background count that's hampering your spells or aiding your enemies.
Here's an example: Jennifer Wu, the Wujen is in a corporate office with some chummers,. The drek hits the fan and goons are on their way so the wujen needs some help. There's not a lot of natural stuff inside this facility, but she has some options. She can call in the decker to crank up the air-ventilation so she can summon a Sylph, use a potted ficus in the corner to summon a manitou, or use the dirt inside the pot to summon a gnome. She can light a fire inside a wastebasket and summon a salamander or she can ask the troll to knock over the water-cooler and summon an Undine (pronounced Un-dee-nee) The GM in this case, noting the weakness of these elements, tells Jen's controller that the force of her summons are limited as the elemental force is weak here. Jenny comes up with a plan, she calls in the decker and has him turn on the emergency sprinkler system, the GM says that eases the limits so she summons a force 5 Undine, saving against drain, she summons it again in Greater form. The goons don't even know what hit them as the driving sprinkler system and raging storm power of the spirit nearly kill half the guards and the rest are weakened and retreat. Ms. Wu, nearly drained gets the frag outta there before the storm hits, saving them from it's wrath. The spirit catches up with her later, although a little worse for wear.
This is a hypothetical situation, however, as Wujen aren't technically allowed to summon without a strong, completely natural element. However, this would make them nearly useless as summoners in most areas of shadowrunner expertise, so I've loosened the rules to accomodate the player by requiring the presence of the element but have the spirit arrive in a weakened fashion.
[Edit] Also, Houngans can make zombies for Loa to reside in, as well.