bitflipper
Not being Canadian, I'm not sure where to even buy a hockey mask in my town. But yeah, I think I'll keep an eye out for one. I already own a machete.
Prior to that suggestion, my leading idea was placing a sign in my yard facing that house, which reads "I know who you are and I know what you did". Or maybe just "I know where you live".
Heh. Years ago I used to keep an insane amount of cash in a lockbox hidden in my apartment. I was so paranoid about someone finding it that I put an angrily scrawled note in there saying "I'M WATCHING YOU RIGHT NOW. I KNOW WHO YOU ARE." In the end I just put the damn stuff in the bank.
On a serious note however, maybe you could try putting a sign up saying that you know who did it and that if they would just return the drives intact, no further action will be taken? There is always the small chance that whomever has those drives has fired them up, seen what an insane amount of work there is on them, imagined themselves in the same boat (I know, it's a long shot that they have ever done anything worthwhile with their lives and can relate to losing work) and are currently feeling a little crappy and toying with the idea of getting them back to you somehow? Stranger things have happened.
The other alternative, if you are more than 50% sure it was your neighbors, would be to wait for them to go out and then stick an unsigned note through (or on) their door saying that you know they ripped you off and that you would rather not involve the police but that you have video of them doing it and that if they return the gear in full then nothing will come of it. Either they will have no idea what you're talking about and no idea who you are, or they will know exactly what you're talking about and start seriously weighing up their alternatives. In that case, if they have any brains then they'll give you back your stuff.