I have a Cisco SG102-24 Small Business unmanaged switch, and I needed to know if it would allow vlan tags to pass through it, even though it is unmanaged. I went to the Cisco web site, and checked out the data sheet, which had no mention of 802.1q, or even the letters VLAN. Probably because it cannot set any ports to specific VLANs.
To figure this out I installed the SG102 in between two switches that had VLANS configured on them. Then, I forced the ports connecting to the SG102 into trunk mode. I then sent pings across from the outside switches, and they came through. To verify that it will keep the VLANs separate, I changed one of the hosts on the outside switches to a different VLAN, and as expected there was no communication between VLANs. Once I discovered that worked, I tried to enable dynamic desirable trunk negotioation on one of the outside switches. Turns out the SG102 will also negotiate port trunking using the dynamic trunking protocol!
Even though it is an unmanaged switch, it does pass on VLAN tagging, and performs trunk negotiation.