For the following, Evernote will open and your text files will be in there as Evernote notes. It certainly works for TXT, RTF, DOC(X), other filetypes untested.
Windows:
- Select all the text files you want in Evernote.
- Right click on them.
- Go to "Send to".
- Click on "Evernote".
Mac:
- Select all the text files you want in Evernote.
- Right click on them.
- Go to "Services" (on the bottom).
- Click on "Add to Evernote".