Try sfdoc -k <keyword>. For example,

bash$ sfdoc -k velocity
sfexgr: Exact group velocity in VTI media
sfchebvc: Post-stack 2-D velocity continuation by Chebyshev-tau method.
sfagmig: Angle-gather constant-velocity time migration.
sffourvc2: Velocity continuation with semblance computation.
sfdix: Convert RMS to interval velocity using LS and shaping regularization.
sfconstfdmig2: 2-D implicit finite-difference migration in constant velocity.
sfpwdix: Convert RMS to interval velocity using LS and plane-wave construction.
sfdixshape: Convert RMS to interval velocity using LS and shaping regularization.
sfpveltran: Slope-based velocity transform.
sfvelcon: Post-stack velocity continuation by implicit finite differences
sfvscan: Velocity analysis.
sfvelmod: Velocity transform.
sfpreconstkirch: Prestack Kirchhoff modeling/migration in constant velocity.
sfunif2: Generate 2-D layered velocity model from specified interfaces.
sfunif3: Generate 3-D layered velocity model from specified interfaces.
sffourvc: Velocity continuation.
sfimospray: Inversion of constant-velocity nearest-neighbor inverse NMO.
sfvelcon3: 3-D finite-difference velocity continuation on a helix

If some program description attracts your attention, run the program without arguments for a self-doc, then follow examples in the USED IN section to observe how it was used. Alternatively, use the web interface.
“sfdoc -k .” produces a full list of all programs.