Hi,
Welcome to the wonderful world of SEOmoz!
The site seems to have a decent approach to SEO. Although its always worth reading the beginners guide as mentioned. I'd also agree with Ryan regarding the multiple entrances to the site, although i'd use a 301 to do this rather than canonical. I'd recommend re-directing the site to the www.allianceconcretepumps.com/ version. Have you verified webmaster tools yet? You will find this very use full indeed and can also select in webmaster tools which site version is displayed i.e. the www.allianceconcretepumps.com/.
What I did notice is that some images are missing alt text (the descriptive image text used by screen readers/search engines), one example of this can be found on your home page - the image in the 'May part specials, another is the images in 'featured concrete pmp' and 'testimonials' at the base.
If you view the site as googlebot (download the moz tool bar, you will be able to do this easily once the moz toolbar is installed), then look at the page you can see that some potential seo value is lost by not having the alt text added in. Viewing as google bot will also highlight other potential areas for improvement.
personally, i'd also see your meta description tag as being overly keyword rich, try to make this a little more engaging and descriptive rather than keyword stuffed.
You could also do with building some links with some varied anchor text from a broader range of root domains. Check out some of the blog post on SEOmoz for link building tips.
