Anyone know what, if any, industry standards are supported by the Juniper SSL VPN devices? Like any of the VPN Consortium standards (http://www.vpnc.org/vpnc-ssl-features-chart.html)?
In particular I'm wondering if Network Connect and Pulse the only clients that can be user to log into a Juniper VPN (SA series in my case).
Those features don't specify interoperability, they just describe capabilities and vendors ability to meet them.
To answer your more specific question, we don't support any 3rd-party client connections to the SSL VPN appliances. Is there some feature you're interested in that we don't already offer?
Starting with 7.0 you can use an IKEv2 client to connect with certificate-based authentication; with 7.1 you can use username and password for your IKEv2 clients if that is what you were looking to know.
Otherwise, as KB_Fan stated, there is no other client interop available.
In addition, the Juniper Networks SSL VPN meets all the checkboxes that are shown on the tables.