Can vows made by women nowadays still be annulled by father or husband (until sunset of the same day), as described in this week's parshah (mattos), or is this a practice of biblical/talmudic times only?
כל הנודר אף ע"פ שמקיימו נקרא רשע ונקרא חוטא
Anyone who vows, even if they keep them, is called evil and called a sinner
It can be done nowadays [as Double AA answered], however one should check after doing it with a competent authority. As there are a number of details that restrict this nullification, including that the vow be "between husband and wife", or עינוי נפש "suffering", and that the husband did not "affirm" מקיים the vow.