Following some fan mail yesterday, I think I'm going to continue this thread of prayer resources for a couple of days more at least.
These days, I rarely write my own prayers. There are so many established prayers with deep and sensitive wordings, and written in the rhythm of human speech, that it makes sense to use those and take what time I have for worship preparation and put it into the sermon. These are not usually new published prayers, which too often look and read like free verse, are breathy in their self-satisfactions and stumble into cliche. I'd rather take something old and tweak it; say, if there are too many generic men or fathers.
One of the reasons I set up hymnsofthespirit.org was so that I could share the liturgical elements I scanned for easier searching. (Despite it being dedicated to the hymnal, the site now is really for the associated Services of Religion.)
I'm looking for other similar resources, and I think I found one: Morgan Phelps Noyes's 1934 Prayers For Services: A Manual For Leaders Of Worship.
This work obviously isn't a denominational work, but comes out of that thought-filled mainline Protestant stream, which included Episcopalians, Presbyterians and Unitarians. Several prayers from the then-standard Unitarian hymn-service book and James Martineau, with Anglo-Catholic Pearcy Dearmer and the evangelical-tinged YMCA being the other bounding limits. I think it has promise, even if I might not think every prayer is appropriate.
Plus, it's large and well-organized. The table of contents and index are useful alone for inspiring sermon themes. The selection of opening words is well-chosen, and includes occasions outside the liturgical church year, like Children's Sunday.
There are, of course, many prayers. But one feature I look forward to using are "addresses to deity." Fundamentally, collects are modular. You might remove the first part where you address God and replace it with something appropriate. Each section of the book ("The Prayer of Invocation," "The Prayer of Thanksgiving," "…Petition," "…Intercession," "…for Special Days and Seasons," "… for the Funeral Service") starts with these open-ended addresses. This can also be useful for prompting prayers that would be better for you to write or heavily adapt.
Lastly, the prayers are well-cited and the bibliography seems ripe for further exploration. I know I will.