Several major collections of surface meteorological observations are

The Global Surface Network (GSN): The GSN provides a global reference network of land surface observation stations and mid-oceanic islands that can be used to detect and quantify aspects of climate change. The network has an approximate density of one station per 250,000 square kilometers. It is optimized for temperature observations and for suitability of stations for climate analysis.

The Integrated Surface Database (ISD): contains the full suite of meteorological variables (e.g., temperature, precipitation, winds) from land stations.

The International Comprehensive Ocean Atmosphere Data Set (ICOADS) 1662-present: contains the full suite of meteorological variables and also sea surface temperature from marine platforms such as ships and buoys.

The International Best Track Archive for Climate Stewardship (IBTrACS) 1851-present: contains tropical cyclone location and intensity reports from around the world.

The International Surface Pressure Databank (ISPD) 1755-2010: contains surface and sea level pressure observations from three components: land (largely from ISD and also 43 other national and international collections of pressure observations), marine (largely from ICOADS), and tropical cyclone pressure reports from IBTrACS. Discussion Page.

Annual Maps of the ISPD version 3 station component can be browsed at http://www.esrl.noaa.gov/psd/data/ISPD/
Annual Maps of the ISPD version 2 station component can be browsed at http://www.esrl.noaa.gov/psd/data/ISPD/v2.0/

The International Surface Temperature Initiative surfacetemperatures.org is assembling station temperature and other meterological variables with an emphasis on traceability and provenance through development of a global land surface databank.

The Hadley Integrated Surface Dataset (HadISD) 1973-present: is subset of selected stations from the Integrated Surface Database (ISD) for selected variables being quality-controlled by the UK Met Office Hadley Centre.   Take part in a discussion of data quality control issues.

The European Climate Assessment & Dataset (ECA&D) ~1900-present: contains daily land station observations for >7500 stations throughout Europe and the Mediterranean. The dataset has 12 meteorological elements for which derived products such as trend maps and anomaly maps are created. Also a gridded version (E-OBS) is available. Discussion page.

The Southeast Asian Climate Assessment & Dataset (SACA&D): contains daily land station observations for  stations throughout Southeast Asia. The dataset has 10 meteorological elements for which derived products such as trend maps and anomaly maps are created.

discussion of Data Rescue to contribute to these and other collections are found on the Data Rescue pages