Earlier this year I went to a 10-day silent meditation retreat to learn Vipassana (insight) meditation. I had been meditating for close to a year prior to going but the retreat was great because the meditation technique progresses each day and you leave the retreat with the tools to integrate the teachings into your everyday life. Not to mention the retreat is totally free with participants being able to make an optional donation at the end if they want to pay it forward so others can learn.
Overall, the retreat had a profound impact on my life. I'd also highly recommend serving/volunteering at the course.