When the ancient Rabbis want to etch something in memory and make it part of regular practice and belief, they stick it in the siddur. I cannot specific cite a source for this pronouncement, which I included in a recent dvar torah — although Berakhot, the Babylonian Talmud’s Tractate on Blessing, is one source that lends lots of support to this idea.
The prayerbook is such a rich environment, but it’s easy to miss most of it as we pass through. We often treat the siddur like our own hometown: we can imagine why others are fascinated and seeking to learn more, but we just want to traverse it to get wherever we’re trying to reach; a travel guide for the place we’ve been living for decades seems beside the point. Additional teachings that have developed over the centuries, to explain why things are (or are not) in the siddur and elaborate on ideas contained in the prayers, can be terrific resources, though.
Here are a few:
- The dvar torah on Parashat Re’eh, mentioned above: The Commandment to See
- Small archive of Divrei Tefillah, words about prayer, produced by congregants at Congregation Rodfei Zedek (Chicago); dvar by Rebecca Milder is quoted in above
- Elaborate Making Prayer Real website, with articles and webinars and more; related to book by Rabbi Mike Comins, released in 2010 (and frequently quoted on THIS blog).
- Re-recommend exploring something along the lines of “Map Your Heart Out“
"A Song Every Day" 
Virginia, thanks for this.
Can I share 2 sources that this causes me to reflect on?
One, long standing powerful to me, is the paradigm effected in Rosenbergys Jewish Liturgy as a Spiritual System.
The other is only recently discovered. Because Abe has…if nothing else….articulated some of the important questions, I’ll introduce his “program” here: http://beureihatefila.com/index.html
He offers weekly classes via a WebEx style presentation, and charges nothing. His presentations are just that…no interaction is invited, and the style is very narrow. But, his work is going to be of some interest, inevitably.
So many thanks for your continued work.
Ira Zukerman