Atbara is a suitable base for trips to the nearby Pyramids of Meroe, which are located just off the highway near a village called Bajrawiyya. take any bus heading to Shendi or Khartoum, and hop out when you see the pyramids rising from behind the dunes on your right after an hour or so. Ask your driver or kamasaari (bus conductor) for "Al-Ahraam", and make sure all the passengers know where you are heading...if you don't see them, someone might remember!
You can stay overnight in Bajrawiyya, either with a local family, or camping in the dunes...but a better oprtion is to return to Atbara, or continue on to Shendi. Buses on this road are frequent, and they can almost always find space, especially for a khawaja!
Every week, there is a train from Khartoum to Wadi Halfa, arriving there in time for the boat to Egypt, returning a few days later with newly-arrived apssengers off the boat. The trip all the way from Wadi Halfa to Khartoum takes in excess of 40 hours, is very uncomfortable and slow, so Atbara is a good place to break the journey. Just for an idea of how slow it is, a bus between Atbara and Khartoum takes 4 hours on a good tarmac road, while the train takes 12 hours...bus and train cost the same, so it is difficult to see the advantage of staying on board for the last part of the train journey. Atbara has several hotels in the bus station, is a pleasant place to prepare you for the chaos of Khartoum (or a place to recuperate after a few days in that city), and you can also visit the Pyramids of Meroe, just an hour away by bus.
Most visitors to Atbara treat the place as nothing more than a place to change transport, and try to leave almost as soon as they arrive. Many do not realise that atbara is situated where the Nile and the Atbara rivers meet, and that down by the waterfront are some great watery views. You can take a ferry over to the opposite bank of the Nile to get an overall picture of the layout...it is a very local ferry, with lots of braying donkeys, laden with fresh milk, jostling for space with foot passengers and the off vehicle. There is absolutely nothing on the other side, apart from a road off to some distant villages, so the only reason to take this ferry is for the views of the river from the boat. Bring some insect repellent, especially near sundown, as the midges there tend to swarm around anything that breathes, getting into every orifice! If you can't find your insect repellent, wear a veil!!