Joseph Goldstein wrote an article on karma and cause and effect that looks at the traditional Buddhist teachings on karma, including discussion of related ideas like rebirth that are not widely accepted in the West. He pointed out that these ideas are not necessary for meditation practice, or even for awakening, but he felt that it’s important to realize they are an important part of the Buddha’s basic teachings. You can find his article here: Cause and Effect Goldstein was recently interviewed on these same topics by Dan Harris and you can view that video interview here: Karma and Your Past Life
Gil Fronsdal has a transcribed talk on karma, cause and effect, and intention posted on the Insight Meditation Center website. The talk also focuses on the effect of the choices we make in our lives and the ways in which mindfulness can impact our choices. You can find the transcription and the audio of that talk here: karma and Intention
Jack Kornfield takes a look at karma and intention and their relationship to habit formation in an article posted on his website. The post includes a description of habit formation and the way it modifies the synapses in our brains, and also the view of our intentions as the planting of seeds. You can find his post here: Karma and Habit