The seqinR package for the R environment contains utilities to retrieve and analyse biological sequences.
Documentation is available here. This is version 2.0-7 of the seqinr manual.
We have moved seqinr sources on R-forge in summer 2008. The old seqinr web site is here, but please note that some items are now obsolete in the old web site. For instance, if you want to browse the source repository, now it's here thanks to R-forge's tools. We are planing to move progressively the old web site to this new one.
The project summary page you can find here.