Other LADSPA Plugins
Computer Music Toolkit (CMT)
These are available from the CMT page on the LADSPA site, and contain a lot of useful things such as delays, filters and an implementation of the popular open source ‘Freeverb’ program.
MCP / REV / VCO Plugins
A set of plugins by Fons Adriaensen. They're quite specific to AlsaModularSynth, but can be used in other hosts. The Moog VCFs in the MCP set are excellent - both in terms of quality and stability. The VCO plugins are bandlimited but use a different approach to achieve this.
A large set of really nice effects including various compressors, distortions, reverbs and other wacky things. Also includes another set of bandlimited oscillators - these have a softer sound than the BLOP ones.