Urd has very powerful magic. In the beginning of the Manga series, it was even stated that Urd was more powerful than Belldandy, although we're unsure of that statement as of the current point and time. Unfortunately, with great power comes great responsibility. Anyone who's seen Urd at all knows that she has no sense of responsibility what-so-ever. Well, at least not a whole lot anyway. Her precision is horrible, which is why her powers are limited, and why she's a Second Class Goddess.
Urd's most common magical attack is "Urd's Bolts." You see those on a number of occassions, especially when she's trying to blow up Skuld or Keiichi for pissing her off. It seems to be a rather powerful attack, since it always has a nice toasting effect on whoever it hits.
Other attacks or magical powers include the basic Goddess abilities. She can float or fly through the air on a broom or vaccuum. She's able to cause objects to do as she pleases (such as spinning a spoon or what-not [it was attempted in Volume 2 of the OAVs, "Midsummer Night's Dream," only Urd failed miserably]). She's also able to cast spells on others (which is usually with the help of her potions).
A lot of what Urd accomplishes is done with her potions or pills. Her room is filled with them, and she meticulously counts and sorts through them every night (which is why she knew when Peorth had secretly stolen one of her "Seeds of Love" [Manga]). Another of her pills, "Sweet Project A," tracks down and exposes crimes that someone has committed (she was able to make Skuld confess that she took the motherboard out of Keiichi's computer as well as confess that it was she who spilled tea on his report [Manga]). It's one of the few things Urd's actually devoted to, and they always work (sometimes a little better than everyone would like).
Despite her magical screw-ups, she seems to actually have great talent with her potions, and serves as the doctor of the house, often taking care of Goddess illnesses, as well as helping to solve problems. Unfortunately, as is usually the case with Urd, her potions can also hinder a situation more than help them.