  We review some aspects of the dramatic consequences of supersymmetry breaking
on string vacua. In particular, we focus on the issue of vacuum stability in
ten-dimensional string models with broken, or without, supersymmetry, whose
perturbative spectra are free of tachyons. After formulating the models at
stake, we introduce their unified low-energy effective description and present
a number of vacuum solutions to the classical equations of motion. In addition,
we present a generalization of previous no-go results for de Sitter vacua in
warped flux compactifications. Then we analyze the classical and quantum
stability of these vacua, studying linearized field fluctuations and bubble
nucleation. Then, we describe how the resulting instabilities can be framed in
terms of brane dynamics, examining in particular brane interactions,
back-reacted geometries and commenting on a brane-world string construction
along the lines of a recent proposal. After providing a summary, we conclude
with some perspectives on possible future developments.
