A certain American Catholic speaker likes to point out that the psalm tells us that God laughs. He reference Psalm 2 - and I always find this an odd point of reference for the happy-go-lucky image of God. The King James has it thus:
"He that sitteth in the heavens shall laugh: the shall have them in derision.Then shall he speak unto them in his wrath, and vex them in his sore displeasure"
Now, we know the psalms speak out of the Humanity of Israel (though also the General Instruction for the Liturgy of the Hours explains that 'in the psalms Christ [is] calling out to his Father or the Father [is] speaking to the Son - the psalms are then taken as the prayer of the church: sometimes it is the sinless Christ speaking, and sometimes the pilgrim church). The psalm does speak of trust in God and his providence, but one must get beneath the context of the people writing and singing this hymn to appreciate it's beauty and relevance.
Back on topic, divine laughter is probably more clear in the case of Abraham and Sarah's annunciation of the birth of a son. Now they were both pretty old - Sarah is well past bearing children in the natural course of things - so when God starts saying that next year she'll have a son she can't help but laugh at the prospect. So God commands the boy be names Isaac, a name which derives from laughter. This almost seems like a cruel taunt by God that Isaac will be a constant sign of their lack of faith in the Almighty's word. It reeks of negative humour to tear them down. But they obey God, and a couple of chapters later, Abraham names the Child Isaac, and Sarah says:
"God hath made me to laugh, so that all that hear will laugh with me."
There is a joy here - 'God is so marvellous look what he can do!' ''God exceeds our expectations'' (rather than 'our doubt reduced god'). God uses our failings to bring glory and love into our situation.