Hey Troy,
So I've been doing a lot of research on subscription services recently because they sound fun. I actually just made my first order from Craft Vapery. Here are a few ones I found that offer samples:
Drip Club offers a "Hero Box" for $24.95 which include 4 x 15 mL bottles. I'm not sure if Drip Club has a subscription service anymore, but they come out with new Hero Boxes every week. You can see what you're getting before you get it, too.
VapeCrates offers a sample crate for $25.00 (free shipping) which includes 60 mL of juice and "glorious goodies" (?). They offer various subscription services, too.
Those are the only true "sample" options I remember running into. However, most of these companies have fairly liberal cancellation policies, so you might consider just ordering a month's worth from one and canceling your subscription if you don't like it. That's what I'm doing with Craft Vapery. Also, check out NicPick. They seem to offer the best value in terms of mL juice per dollar. Either them or ZampleBox.
Hope that helps,
N8