Orrery от Nidias

Orrery replaces your new tab with the solar system as it actually is at this
moment.

The background is not an animation on a loop - it is an ephemeris, computed in
your browser every frame. Planet positions come from JPL's Keplerian element
set, the Moon from Schlyter/Meeus lunar theory including the main
perturbations, and Io, Europa, Ganymede and Callisto from Meeus's Galilean
satellite theory. Hover any planet for its distance from the Sun, its distance
from Earth and its ecliptic longitude; hover Earth for the current Moon phase.

Two distortions are deliberate, because no screen holds 30 AU and 2400 km at
one scale: radial distance is compressed, and moon orbits and body diameters
are enlarged. The angles are untouched, so the arrangement you see is the real
one. Nine other moons use mean circular elements - correct orbital periods, but
an approximate epoch phase - and say so in their planet's readout.

Also on the page:

• A search bar with selectable engines and !bang prefixes (!yt, !gh, !w, !g).
  Type a URL and it navigates instead of searching.
• Your own quick links.
• Your own RSS and Atom feeds below the fold, round-robined across sources so
  one busy feed cannot fill the screen, cached so the page opens instantly.
• A time control, if you want to wind the sky forward and watch it move.

Everything is configurable and everything stays on your machine.