I can find various speeds and estimated durations listed at numerous places but none specifically describe the frame of reference.
Possible options as example of kind of answer I expect.
- Local Galactic cluster
- Distance quasars
- The cosmic background radiation?
--------- UPDATE ---------
Thanks AIB and voithos. Lot of reading for me.
Though technically, I still don't have an answer that meets the following criteria.
- rotational velocity(average preferably) of sol around best estimate of center of Milky-way galaxy.
- publicly available reference(I don't have immediate access to some of the books given)
- frame of reference external to Milky-way galaxy.
As I note below the only reference (wmap5basic_reprint.pdf) I can read that uses an external frame of reference doesn't specifically state the vector is rotational (despite wikipedia article assuming such). The topic is barely touched on in that paper.
I realised the speeds are variable. What I had not realised is that the whole idea of a (relatively) clearly defined x orbiting y system doesn't really scale up well from the local solar system to the galactic scale. The galaxy is more like a whirlpool or tornado compared to the "clockwork" appearance of the solar system. Although both the solar system and galaxy are constantly(very slowly) changing "fluid" rotational systems, the galaxy is obviously far more fluid than the solar system. Also we have not yet been able to observe anything about it's center.
Or in other words, we are not "orbiting" the galaxy, we are part of the galaxy.
I suspect the topic is more in the realm of "fluid dynamics" than "orbital mechanics"
I've accepted AIB's answer as the most enlightening to me personally. Also, it would appear I have wiki-sidebar blindness. Apologies for that.
The paper referencing the speed relative to the CMB, as mentioned in wikipedia article can be found here http://cmbdata.gsfc.nasa.gov/product/map/dr3/pub_papers/fiveyear/basic_results/wmap5basic_reprint.pdf The relevant section appears to be 7.3.1. "... implies a Solar System peculiar velocity of 369.0 ± 0.9kms-1 with respect to the CMB rest frame." Although it's not obvious to me what vector that velocity is along.
Though Dipole Anisotropy in the COBE DMR First-Year Sky Maps gives a specific velocity(including vector) for the local galactic group in relation to the CMB rest frame "implied velocity of the Local Group with respect to the CMB rest frame is 627 +/- 22 km/s toward (l,b) = (276 +/- 3 deg, 30 +/- 3 deg)."
Other reference frames that are external to the local galaxy are "The Supergalactic coordinate system"