This is a really simple strategy, but it is also kind of good. On money maps, build huge amounts of hatcheries. Get a lot of workers to mine minerals and gas. I tend to get about 20-30 hatcheries. When you get enough gas mutate em' into lairs then hives to produce larva's faster. Upgrade hydralisks to the max and get hydralisks. Build huge amounts of overlords, and I mean huge. Think like 80. Then send your hydralisk to attack your opponent. Move your mass overlords in front of the hydralisk to block some hits. Also try to drop a few lurks. But just a little, so that your opponent might think your dropping units. Keep on send massive waves of attacks and also try mutalisk to demolish workers.
The Guardians And Lurkers
Most people don't use lurkers, but why not? They got well with guardians and devourers. Just get massive guards and devs and drop some lurks behind minerals. Your opponent of course will try to save the workers and attack your lurkers. If they do, send in the guards and devs. They either have to kill the lurks or guards attacking their base. If they have mainly ground, this strategy will work well.
Sure mutalisks get killed by templars, marines, battle cruisers, corsairs, valkyries, archons, and numbers of units, but they are fairly fast. On money maps, get massive hatcheries and produce mutalisks. Once you get a swarm of them, use one to patrol from 1 side of the screen to another. Then select all the other mualisks and tell the to follow the patrolling one. Once all mutalisks are assigned to one mutalisk, move that one mutalisk near workers. Then you must sacrifice that mutalisk to kill workers immediately. Tell 12 mutalisks to kill the one muta then all the mutalisk will start attacking everything around them. Of course this strategy workers with scouts and wraiths, but is is VERY easy to get massive mutalisks on money maps.
Zerg Tactics - Decoy Hatchery
By mid to late game, don't be afraid to plop down a Hatchery near your allies or team staging area (usually the center), even if it's not near resources. This will give you another troop factory; even better, it will let you build a Nydus Canal from your most defended area to your allies' bases or to the front lines. It doesn't cost anything. At worst, it's a decoy that your enemies will waste time attacking.
Zerg Tactics - Scourge Bombing
Use them against Carriers and Battlecruisers. You should always have at least eight or ten of these mini-fighters hot-keyed and waiting in reserve. Two groups are even better. When you get attacked by a superclass ship, grab a Scourge squadron and aim it directly at your target. A few will get picked off, but as long as five or six hit the target, you'll take it out.