Recently visited Aurangabad and covered most of the interesting sites around. Best time to visit Aurangabad would be after monsoon when terrain is green or in winter so that one could roam around easily.
Lonar - This is the pre-historic site of a meteor which crashed on earth some 50, 000 years ago and formed a large crater (few hundred meters in diameter) in the ground. Though there are other impact craters in the world but this one is the only in besalt rocks. The pH value of water in the lake which has formed in the crater is 10.7 which points to its alkaline nature. There are no living organisms in the lake and even trees whose roots get into the lake water dies. This site is must visit for scientifically inclined and for others just for curiosity sake. The lake is beautiful and its first look will surely take your breath away. It is best enjoyed before suset. One could go down upto water level and experience the water which is harmful. There is also a temple of kamalja devi at the edge of lake. Apart from lake one could visit daityasudan surya mandir which is a small ruin of Khajuraho like temple, Gaimukh which is a perennial source of fresh water with some masonary work done by Peshwas to channelize the water, motha maruti hanuman temple which is a temple built around a magnetic rock supposedly formed from meteor effect. One could visit retired principle of local school who accompanied various scientific expeditions in the region and has some research material with rock samples. There is an MTDC resort near the crater and one could stay there for its absolute peaceful surroundings. Lonar is ~160 km (3.5 hrs) from Aurangabad which is the closest big city.
Paithan - Paithan is famous for its hand-woven sarees which sell for, hold your breath, more than Rs 10k per saree depending on the quality. Other attractions are a masonary dam over serene Godavari river which forms a huge lake on the back of the dam and a huge garden on the lines of Brindavan garden in Mysore. The dam is pretty long with a promenade around it. Walking there in the evening could be quite gratifying. The garden far exceeded our expectations. Its well-maintained, well-lit and has lot of fountains. Everyday there are musical fountain shows starting at 7:15 PM which also show puppets dancing on bollywood songs. The whole atmosphere is quite good. Paithan is around 56 km (1 hr) from Aurangabad. Plan to come to Paithan only in the afternoon and remain till late evening.
Ajanta & Ellora - These places are well-documented in various mediums so wouldnt elaborate much. The caves paintings and sculptures are divine. Avoid taking ITDC tours which simply rush through the sites and most of the time is spent in driving to the locations. I would also suggest to do some research about the art over there from various mediums so that you could appreciate the art over there. I would also suggest to wear sandals to Ajanta because at most of the caves you are supposed to take off your footwear.
Dualatabad is a fort over a hill and views from the top are breathtaking. Give ample time to climb up and coming down so that you could appreciate the views o/w fort is in ruins. You could also hire a guide who would take you around the important corners of the fort.
Bibi ka Maqbara was built by Aurangzebs son for his mother and is a poor imitation of Taj Mahal but still worth a visit.
Panchakki is a simple funda of pouring water over blades of a fan like arrangement which has a chakki on top used to grind wheat in olden days. There are small tanks with water and lotsss of fish whom you could feed but not feed them to yourself :-) This too is worth a visit but wont take much time.
Ghrishneshwar temple is seat of one of jyotirlings of Shiva. few kms away from Ellora caves. No need to stess on its importance.
You would be surprised to know the most essential thing we missed in Aurangabad. A Torch !! Yes, a simple torch will come handy for you in Aurangabad, be it trying to look at sculptures in unlit Ellora caves, climbing the Daulatabad through a small patch of claustrophobic staircase or promenading in unlit portions of garden in Paithan after dark.
Hope this review is helpful. Please send message for any more information.