General synonyms:
* Chuckling
* Giggling
* Chortling
* Grinning
* Smiling
* Snickering
* Tittering
* Wheezing (with laughter)
* Guffawing
* Roaring
* Howling
More specific synonyms:
* Joyful laughter: Beaming, exhilarated, mirthful, gleeful
* Nervous laughter: Awkward, fidgety, uneasy, sheepish
* Condescending laughter: Derisive, mocking, scornful
* Forced laughter: Artificial, strained, insincere
* Hysterical laughter: Uncontrollable, manic, wild
* Soothing laughter: Gentle, calming, comforting
* Sarcastic laughter: Dry, ironic, cynical
Figurative synonyms:
* Bursting into laughter: Explode, erupt, erupt in laughter
* A wave of laughter: Ripple, spread, surge, sweep
The best synonym to use will depend on the specific context of your writing.