Take a piece of the hose to the hardware store and get a platic insert that will fit snug inside of it. If it is a tight fit, you may not even need to clamp it with a hose clamp. The fittings are barbed and come straight, tees, and 90's.

i laughed a little bit when i read the title of the thread, i was thinking- wow! my soaker hose leaks too!

but seriously- what was posted above should work, or try wrapping the area in copious amounts of tape (electrical or duct). because soaker hoses are generally low pressure, tape may hold and may not require a trip to the store.

If the holes/gaps are small enough I can fix mine with super glue.