Oncidium anthocrene Rchb.f.
 

This is an intersting Central and South American species. It ressembles a little some Cyrtochilum and I think it was once classified as one. The flowers are 5 cm across, a good size for an Oncidium. The plants get larger and the inflorescence stems longer than what is seen in my picture.
Oncidium anthocrene Rchb.f. on Flickr - Photo Sharing!