Rosetta Design and Chimera energy minimization to refine small proteins: http://rosettadesign.med.unc.edu/
In general GROMAC has a good tutorial for refining proteins without NOE data: http://www.gromacs.org/@api/deki/files/203/=tutorial.pdf
Also, there is a paper explaining other good methods to refine protein structures without NOE data: http://journals.plos.org/plosone/article?id=10.1371/journal.pone.0108888
In this paper they introduce STAP algorithm which can be run here: http://psb.kobic.re.kr/NmRe/index.cgi
Other algorithms: RECOORD, AMBER.