  The s-wave interaction is usually the dominant form of interactions in atomic
Bose-Einstein condensates (BECs). Recently, Feshbach resonances have been
employed to reduce the strength of the s-wave interaction in many atomic
speicies. This opens the possibilities to study magnetic dipole-dipole
interactions (MDDI) in BECs, where the novel physics resulting from long-range
and anisotropic dipolar interactions can be explored. Using a variational
method, we study the effect of MDDI on the statics and dynamics of atomic BECs
with tunable s-wave interactions. We benchmark our calculation against
previously observed MDDI effects in $^{52}$Cr with excellent agreement, and
predict new effects that should be promising to observe experimentally. A
parameter of magnetic Feshbach resonances, $\epsilon_{dd,\text{max}}$, is used
to quantitatively indicate the feasibility of experimentally observing MDDI
effects in different atomic species. We find that strong MDDI effects should be
observable in both in-trap and time-of-flight behaviors for the alkali BECs of
$^{7}$Li, $^{39}$K, and $^{133}$Cs. Our results provide a helpful guide for
experimentalists to realize and study atomic dipolar quantum gases.
