CSV, ODS, JSON (.json, .geojson, .topojson), SHP, HTML
GDAL - Geospatial Data Abstraction Library - a translator library for raster and vector geospatial data formats that is released under an X/MIT style Open Source license by the Open Source Geospatial Foundation. As a library, it presents a single raster abstract data model and vector abstract data model to the calling application for all supported formats. It also comes with a variety of useful commandline utilities for data translation and processing.
ogr2ogr - converts simple features data between file formats
Open Source Geospatial Foundation - OSGeo was created to support the collaborative development of open source geospatial software, and promote its widespread use.
QGIS - is a cross-platform free and open-source desktop geographic information system (GIS) application that provides data viewing, editing, and analysis capabilities.
Mapbox - mapping platform - repos on github
Tabula is excellent for PDF scraping, however its a resource hog:
Scraperwiki is mentioned in another response, but sadly they've moved on to charging, however you can set up your own version from their sourcecode:
Google Drive is great for easy storage, sharing/collaborating, and converting to/from other formats.
I can't emphasis how great drive is for alot of the work I do. You can even use it for scraping HTML tables into Google Spreadsheets, utilizing the
importHTML function; read more here:
Web Scraping with Google Docs:
geojson.io is amazing for a number of things:
easily convert kml into geojson, topojson, csv, and shp
github/gist integrations allows for easy storage
view maps instanteously upon upload
mapshaper also provides easy format conversion from shapefiles
ogr2ogr web client - convert gis data formats
heatmap.js - Dynamic Heatmaps for the Web
datahub.io for data storage/sharing
ckan for running your own data portal
Open Data Kit - (ODK) is an open-source suite of tools that helps organizations author, field, and manage mobile data collection solutions.
data.gov - tools they use, repos on github
Open Data Tools - Tools to Explore, Publish and Share Public Datasets
Nokogiri - web scraping library (ruby)
Mapping Cheatsheet - this list has some tools already listed, but in greater detail, as well as more tools, plus information in regards to choosing that apply to your particular data:
US Census Github Tools
Open Data Research Portal
Open Data Guide
Project Open Data - Open Data Policy — Managing Information as an Asset