I've been using the USGS National Map viewer (http://viewer.nationalmap.gov/viewer/) for getting data for QGIS, but the download system is driving me insane. I enter my email address and [sometimes] get a notice that my data will be available in up to 2 days (why so long???) If that email does arrive, occasionally the URLs are linked to a 0 byte file and I'm out of luck.
Is there any other place to get the data? This "click and hope your data arrives in 2 days" system keeps getting me in trouble and behind on my work. I don't understand why I can download multiple GBs of elevation data from USGS on demand but hydro data that's a fraction of the size requires a waiting period.
Edit: I'm specifically looking for hydro, transport and land cover for Kittitas Valley in Washington state. Thanks for the great answers.