So, I've designed my pages for humans and not for search engines. My site architecture is a bit complex, but every page is within three clicks of the home page and I have no hidden or tricky links. While my HTML is messy (an artifact of the editor I'm using), it does validate. I'm not knowingly using any Search Engine Spam techniques; the keywords in my meta tags are all relevant to the content. I generate new sitemaps twice a month and upload them to Google religiously. My site is not static; I try to add new content at least once a week. Finally, my content is by and large unique; so far I haven't found a single site out there doing what I'm doing on anything close to the same scale I am, even though I'm still less than halfway to where I want to be eventually.
And still, Google doesn't seem to know that I exist.
Oh, my main page is indexed; you can google on my website title and the home page comes up. But, so far, none of the primary content (the timetables) seems to be indexed. Using Google's webmaster tools to check my site, only three pages (out of 58) even show up at all and one is a test page which has long since been relocated. And while one timetable does show as being indexed, a google on "timetable Mobile Noxapater" (which should show a hit) returns just nine results, none of which are in any way associated with my site.
Back when I was working out the kinks in my CSS formatting (with the kind help of the members of this forum), the test page did show up on Google's list and in fact, according to my web logs, I got several hits on it as the result of Google searches. But for the past two months--nada. Yahoo is showing several of my pages, as is MSN, but so far I have almost completely managed to elude Google's notice.
I'm not going to obsess over my page rank; as I said, my content is unique enough that it should make a strong showing in any suitably targeted search. But if it's not in their index at all--then what do I do?
Standing by for suggestions, I am...

You say your site is dynamic. Are your URLs long and cryptic like http://www.site.com/site.php?do=view...eb&article=123 or are they short and concise like www.site.com/article123.html ... You may want to play around with mod_rewrite
It seems like your problem is that you don't have enough incoming links to your site. While you've done a tremendous job with on-site optimization, off-site SEO is just as important. You have to get the word out there, and get other sites constantly linking to your articles on a regular basis ... Read up about viral marketing campaigns and write stuff that people are naturally going to want to blog about.

Search engines take quite some time to index all of your pages. The biggest factor, so far according to consensus, is inbound links. This is the "recommendation" your site needs. Also, update the non-indexed pages often so that the crawlers can come back.

You should submit your site to Directories and your inner pages to Deep Links Directories to get free in-bound links.

I don't think you need to resubmit your sitemap 2x/month. Once is fine. But that is not the problem. It is going to take some investigating. Good luck. Ask a lot of questions.