These sites offer several traineeship offers:

• ErasmusIntern: http://erasmusintern.org/
• Erasmusu.com Internship Offers: https://erasmusu.com/pt/emprego-estudantes 
• EURES – O Portal Europeu da Mobilidade Profissional: Candidatos a emprego > Oportunidades destinadas aos jovens: http://ec.europa.eu/eures/home.jsp?lang=pt
• Europlacement: http://www.europlacement.com/en/search-internships
• Great Wine Capitals Global Network: http://www.greatwinecapitals.com/
• iAgora: http://www.iagora.com/
• Instituto Diplomático (Ministério dos Negócios Estrangeiros): https://idi.mne.pt/pt/estagios-01.html
• ISPO: http://www.ispo.co.uk/students/
• Jobted: https://de.jobted.com/praktikum-jobs
• Labour Mobility: http://www.labourmobility.com/about-us/
• Leo-Net: Traineeship offers > http://leo-net.tue.nl/leonet/traineeship-offers/
• PIC Management: https://www.pic-management.com/en
• Praxis European Centre for Project/Internship Excellence: http://www.praxisnetwork.eu/
• Training Experience: https://www.trainingexperience.org/