The University of New England offers online courses (including a lab segment, if you need it); you can
check out their website here. They claim to offer two pathways, a post-bacc and a Master's type program, both aimed at people on the healthcare professionals pathway.
I took one of their chemistry courses at the request of a school that accepted me. I specifically chose UNE because I needed a flexible option: I had less than three months to complete the course, and needed to start and finish on a schedule that didn't match up with a semester schedule.
Their pacing is all self-driven. They suggest that you complete one module per week, and break their courses down to 16 modules. You can access the material at any time of day, and you're not penalized for taking longer than 16 weeks - I think they say that you can take up to one year to complete a course, if you need to. (They also don't penalize you for moving faster - I was doing one module every 2-3 days.)
If you need credits for a lab, there's a lab portion that you do at home. You'll need to order a "LabPaq" (costs around $300 per course) and complete certain experiments through it.
Compared to a traditional undergrad course, I found the UNE online course to be a bit easier. Things seemed a bit more straight-forward, and the self-pacing was pretty nice. Granted, it was a course that I was repeating and I studied for the MCAT multiple times, so I had the benefit of being familiar with most of the concepts already. For a chemistry course, I also found it very biology-driven. There were many real-world correlations, and a surprising amount of organic chemistry and biochemistry present (which was good for me, and will be good exposure in the long run for others, but which might seem a bit overwhelming to some).
The cost seemed very reasonable to me, and made my undergraduate institution seem like a total rip-off by comparison. My course cost less than $1,500, and that includes the cost of the lab materials. They send you the textbook for the course as part of your course fee. Very nice.
I don't know how other schools view UNE's online courses. As far as I know, they're a fully accredited institution, so there shouldn't be a problem with the credits being accepted. It's worth checking to make sure before you start.
Best of luck!