Despite the fact that Evernote and OneNote are generally considered competitors, they can also be used together productively. I work primarily in OneNote 2010 on a Windows PC, for example, but I also have an iPad and an Android smartphone, neither of which currently has a full native OneNote client option from Microsoft. (It's possible to use the OneNote Mobile for iPhone client on an iPad, but it isn't optimized for the iPad's screen size.) I sometimes find it's useful to capture notes on my iPad or smartphone by using Evernote, later copying-and-pasting the notes from Evernote to OneNote. Occasionally, I copy information from OneNote into Evernote, to make lists managed in OneNote available on my iPad and smartphone.
If you need to copy a lot of content from Evernote to OneNote, you may want to explore MobileNoter's Ever2One Converter, a free utility for copying content from Evernote to OneNote. Ever2One includes the option to maintain note attributes (metadata fields) such as author identities and source URLs. It creates a new OneNote notebook titled "Evernote Notes," and a new OneNote section for each Evernote notebook.
If you're interested in moving content in the other direction, the Windows Evernote client can import content from OneNote notebooks.