You can probably get a rate in the 4.25 - 4/5 % range for 15 yr now... what you might want to do is go out to any banks website and go to their mortgage calculator. You know what you're paying now, so just type in what you owe left, how many years you'll do the mortage for , and the new rate. ( any bank can tell you what their rates are today) Once you have that, then compare what you'd be paying in interest if you kept your current mortgage and what the total interest would be on the new mortgage.
3 things to keep in mind.....refinancing is great if you plan to stay in your house at least 5 -7 years. Another, it's good if you can go at least 1% - 1 1/2% less than what you're paying now. The third thing...find out what you'll be charged to refinance....you don't want to have to pay points or pay a huge refinance fee. Our bank refinanced ours for like $ 1300 because they wanted to keep our loan. So they cut their fees. It's worth shopping around.
We had 5.65% (30 year mortgage) and refinanced for 4.75% ( 15 year mortgage). We found that we would save $ 75,000 in interest. So yes, it was worth it. You just have to see for your personal situation if it's worth it.
But I would go out to MSN money, Wells Fargo.....get ideas of today's rates and use the mortgage calculators. Sometimes it's very much worth doing. Good luck !!