gmfsk by OH2BNS (starting at version 0.4) can send logging data to xlog, when clicking on the 'Log entry' button.
Marote (version 2.3 or later), a rig control program for the elecraft K2 by AB6CV does the same when clicking on the 'Log QSO' button.
gpsk31 (starting at version 0.3) can exchange log information when the QSO details dialog is open.
ktrack by LX2GT (starting at version 0.2.1) can exchange satellite information with xlog. In order to do so, you need to enable the 2 free fields with the log-editor. Next, select 'add data to QSO frame' in the last page of the preferences dialog.