  In the general Higgs portal like models, the extra neutral scalar, $S$, can
mix with the Standard Model (SM) Higgs boson, $H$. We perform an exploratory
study focusing on the direct search for such a light singlet $S$ at the Large
Hadron Collider (LHC). After careful study of the SM background, we find the
process $pp\rightarrow t\bar{t}S$ followed by $S\rightarrow b\bar{b}$ can be
used to investigate $S$ with mass in the $20<M_S<100$ GeV range, which has not
been well explored at the LHC. The signal significance becomes meaningful with
a luminosity around a few $\mbox{ab}^{-1}$. Also, we study the prospects of
finding the light scalar at the future 100 TeV $pp$ collider, the $Z$ and Higgs
factories. With similar luminosity, the current LEP limits on the mixing
between $S$ and $H$ can be improved by at least one or two orders of magnitude.
