Miracles don't just happen every day. That's kind of the point. But in Acts the apostles bring the miracle power wherever they go. Healing the sick. Raising people from the dead. Makes you wonder why they don't magic themselves out of trouble more often.
It's A Miracle!
In Acts of the Apostles, signs and wonders are all over the place:
A crazy wind and tongues of fire float into a house. (2:3)
People speak in other languages they don't know. (2:4)
Loads of folks are healed. (3:16)
The ground shakes when the apostles pray. (4:31)
Demons are exorcised. (8:7)
People come back from the dead. (9:40)
Earthquakes break people out of prison. (16:26)
Prophecies are doled out. (19:6)
When was the last time any of this happened to you? We'd say it's all pretty darn miraculous.
In all these cases, a miracle means that something unusual or completely impossible happened. The Bible folks see this as a sign that God is hanging around and still cares about them. God has broken into the natural world and stirred things up (it's not everyday that paralyzed guys get up and walk). This is tangible proof that God is large and in charge, and also that He's on the side of Christians.
It's also a natural continuation of what God started way back in the gospels with Jesus. After all, if God gave Jesus the power to perform miracles and even come back to life, then what's to stop him from doling out a few powers to his most devoted followers? Nothing, that's what.
These days God is a little subtler. Some people still believe in miracles, while others think that everything has to have a rational or scientific explanation. But back in biblical times, people saw miracles everywhere. And without miracles you couldn't possibly claim to have an in with God. Would Peter have succeeded if he just talked about Jesus? Maybe. But raising people from the dead kind of helps give your message that extra little oomph.
In Popular Culture
In Bruce Almighty, God is able to prove his Godliness by guessing the number of fingers Bruce is holding up. Every. Single. Time. Bam.
On an episode of The Family Guy, Jesus comes to dinner and turns the Griffin family's boring food into ice cream.
George Burns proves he's divine in the movie Oh, God! by making it rain. Inside someone's car. Nice one.
In Pulp Fiction, Jules interprets the bullets missing him as a sign from God.
According to the Quran, Muhammad refused to perform any miracles to prove he was from God. It's not like people always believed the apostles when they did.