So does one of mine (I'm trying not to panic), and I hope to read lots of advice here. ;-) I think the Donna Young website under "Recordkeeping" has free transcript forms. Others here have recommended NARS (see "Diplomas & Transcripts") which gives official credit (fees involved).
I'm a procrastinator, and knew I needed some oversight, so I registered our 2 homeschoolers with NARHS (North Atlantic Regional High School), so they'd have an accredited diploma at the end of it all. It's not that expensive, and it was great for my peace of mind. I still had to prepare a portfolio and transcript at the end of each year, and submit the evidence of their having done the work required for each course. This meant that at the end of four years, all that work was there, and credentialed, and the school submitted the information to the Admissions offices of the colleges to which our kids applied. I didn't have to do a portfolio for EACH college application.
Our daughter graduated in 2006, and our youngest son will be graduating this month, and will head off to college in August!
WHEW!
I LOVE the DonnaYoung.org website. It is an excellent resource for beginners (and not so new homeschoolers) for organizing your homeschool.
I have friends that use Homeschool tracker ( http://www.homeschooltracker.com/ ) with good results.