Here is a list of a few Public Spending data on Contracts and Procurement:
Open Ted data store: Anders Pedersen and Joost Cassee have been the EU publication office data on procurement throughout the EU, generating machine readable, ready to process csv data files for contracts with private entities between 2009 and 2013. Transparency at its best.
US Spending.Gov: Excellent website offering data for all sorts of public spending in the US. By selecting 'contracts' in the respective tab, you get to access the relevant data on procurement.
TED Europa: A supplement to the aforementioned Open Ted. This official site provides all the relevant information for bidding or searching for contracts awarded throughout the EU.
AusTender: Contracts and Procurements in Australia.
UK Contracts Finder: What is being bought by the government and costs more than 10000 GBP? You may trace it here. The site can be of great assistance to potential sellers willing to enter the highly competitive market of public contracts.