As per the Fedora 21 schedule [1], Fedora 21 Beta Release Candidate 1 (RC1) is now available for testing. Content information, including changes, can be found at https://fedorahosted.org/rel-eng/ticket/6010#comment:11 . Please see the following pages for download links (including delta ISOs) and testing instructions. Normally dl.fedoraproject.org should provide the fastest download, but download-ib01.fedoraproject.org is available as a mirror (with an approximately 1 hour lag) in case of trouble. To use it, just replace "dl" with "download-ib01" in the download URL.
Since freenode is not working for me (netsplit), I have to ask here - there are no Workstation netinst images for RC1? Also I noticed there is no os/ directory for them.