What poems exemplify a manifestation of feminist attitudes?
As the previous poster notes, the meaning of the word "feminism" has undergone a number of changes, some dramatic and some more subtle.
The two names that stand out for me are Adrienne Rich and Lucille Clifton, although those are just two of many women poets writing feminist verse.
Lucille Clifton's poems are filled with an awareness and even celebration of the commonly shared experiences of (some? many? or most?) women, such as issues surrounding aging, relationships with daughters, and body image. See, for example, her poems "Homage to my hips" and "Homage to my hair." You can find the text online with a simple google search.
Adrienne Rich's poems are often more "brainy," but they're very good, too. You might be interested in reading her poem "Diving into the Wreck" in her award-winning collection of the same name.
A number of poets have written poems with explicit or implicit feminist themes. Some of these poets include Emily Dickinson, Anne Sexton, Erica Jong, Denise Levertov, Nikki Giovanni, and many others. It may be the case that some poems that scholars now consider "feminist" were not intended as such by their authors but have taken on that context over time, since the meaning and expression of feminism has also evolved over the past few decades.