There is no airport in Coimbra, so you must fly to Lisbon or Porto international airports and reach Coimbra by train, coach or car. The distance between Coimbra and Porto is around 100 km and between Coimbra and Lisbon is around 200 km.

By train: There are several daily trains connecting Coimbra and Porto (Campanhã railway station, there is tram line connecting directly from the airport) and Lisbon (Gare do Oriente, closer to the airport, and Santa Apolónia, in the city centre). There are two types of fast trains: Intercidades, with just a few stops or Alfa pendular, which are faster, some being direct.
In both cases, leave at Coimbra B railway station and take the connecting train to Coimbra railway station (this connection is free of charge), in the city centre. On the left side of this Central station you can take a bus (no. 103) direct to the University. (you can find here a map of the city bus lines in Coimbra). If yoy prefer to take a taxi you should do it at the Coimbra B railway station.
To have an idea of the location of the railway stations and the Department of Mathematics, where WNI2008 will take place, follow the links below.

By coach: There are several daily coaches connecting the three cities (Lisboa-Coimbra-Porto). The coach stations are not located in the airports so you must take a taxi or use the public transportation system to reach them. To find information about schedules please look at the Rede-expressos web site (in portuguese).

By car: The A1 motorway connecting Lisbon and Porto goes by Coimbra.