Other LADSPA Plugins
There are a growing number of LADSPA plugins - for the most up to date list, see the LADSPA home page or the Linux Music and Sound site.
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.
SWH Plugins
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.