I will discuss recent studies of two filamentary clouds, the quiescent L1506
region in Taurus and the more massive Orion Molecular Cloud 3 (OMC-3). Both
regions are relatively little affected by local star formation. Radiative
transfer calculations are used to interpret observations of dust continuum
emission, to examine the structure of the filaments, and to search for evidence
of dust evolution. In OMC-3, the observations of dust emission can be
complemented with Spitzer measurements of the mid-infrared extinction. Modelling
suggests that the embedded stars contaminate the extinction signature through
thermal dust emission and scattering, but only very locally. I will also
describe the development of some tools used in these studies, from the
interpretation of spectral lines to the modelling of emission from
stochastically heated grains.
