The 10 meter FM frequencies are good indicators of a band opening on 10 meters/11 meters as well as a potential VHF low band (30-50 MHz) band opening.
29.600 MHz is a good place to start for FM activity, then the repeater pairs
29.620 MHz
29.640 MHz
29.660 MHz
29.680 MHz
are good for scanning during a band opening. I often include down to 29.5 MHz when I do a VHF low band scan for VHF low DX skip in FM mode.
A few years ago there was actually a local logging company that used 29.625 MHz (also logged as 29.620 MHz) for truck-to-truck comms (they were using what they thought was a clear frequency on their export 11 meter CB rigs). Whoops.
I will also say, however, that I hear FM activity on 11 meters when the band is rolling too - and not just the UK FM CB frequencies with the 1.25 kHz offset (27.60125 MHz - 27.99125 MHz in 10 kHz steps). I've heard FM freebander traffic on 27.505 MHz, 27.600 MHz and a couple other frequencies and the stations were US based. 27.600 MHz translates well from 29.600 MHz as a FM calling frequency.
Speaking of FM repeaters - there used to be a linked FM repeater network of four 11m 27 MHz FM repeaters in the Caribbean on 27.620 MHz, 27.640 MHz, 27.660 MHz and 27.680 MHz. They used a +200 kHz offset and even included a 88.5 Hz CTCSS or PL tone. They were linked together (so keying up one would key up the other three and give you simulcast capability)...not sure how they were linked but I imagine it was VHF/UHF.
Here's a video of the network being keyed up.
https://www.youtube.com/watch?v=0pWB17LzsHkUnfortunately it appears that all of these repeaters are now off the air.
There are others, however. Apparently there is a German 11m FM repeater system - input frequency is 26.565 MHz FM and output is 27.405 MHz FM (26.565 MHz is German CB channel 41). In other words, a -840 kHz offset - -
https://www.youtube.com/watch?v=hpfFs4M_U1cI'm sure there are plenty of other 11m repeaters out there. I've seen evidence of cross-band setups in the USA using MURS or FRS / 11m crossband systems. Here's one example of FRS channel 3 - 462.6125 MHz - patched to 11m frequency 26.935 MHz as a repeater system (at least as a proof of concept)
https://www.youtube.com/watch?v=iNMiiyI7WQw
That being said, simplex repeater seems to be more popular, especially in Europe and Russia. They are easy to put together. There are dozens of 11m FM simplex repeaters operating in Russia and elsewhere in Europe. There's apparently one on 27.205 MHz FM in Sweden that features DTMF-controlled playback and other options. The 27.205 FM repeater has apparently been heard/hit in dozens of different countries...
Other known 11m FM simplex repeaters include:
26.965 MHz FM - Channel 1 -
https://www.youtube.com/watch?v=kDI5T-_z7qQ26.985 MHz FM - Channel 3 -
https://www.youtube.com/watch?v=JOWxgc9lRrk - this one has been noted by several other operators too
27.275 MHz FM - Channel 27 -
https://www.youtube.com/watch?v=OgYlzLPH5Jk27.305 MHz FM - Channel 30 -
https://www.youtube.com/watch?v=z1QQlvwFAD0 - possibly more than one on this frequency?
27.415 MHz FM -
https://www.youtube.com/watch?v=r82nX0QuIcw and
https://www.youtube.com/watch?v=wcW1IFBGnsw - assuming this is the same repeater it was heard in Poland and Australia!
27.675 MHz FM -
https://www.youtube.com/watch?v=b6__XiVyTvk