BLOP comprises a set of LADSPA plugins that generate bandlimited sawtooth, square, variable pulse and slope-variable triangle waves, principally for use with one of the many modular software synthesisers available.
They are wavetable based, and are designed to produce output with harmonic content as high as possible over a wide pitch range.
Additionally, there are a few extra plugins to assist in building synthesis networks. Full details can be found in the List-o-Plugins
Cheapskates like me who don't have a real analogue synth!
But seriously, these plugins won't be much use to you if you have some hardware lying about that does the same thing. However, there are some advantages in using a modular softsynth - namely flexibility. You can connect things together any way you like, in the same way that can be done with the old and new modular synths.