As always, you should test thoroughly before you even think about using any of these tools in production. Read the standard disclaimer and the FAQ page, and please tell me if you have any reproducible problems.
Links to the individual tools are available to the left. Here are the sections I've split the utilities into:
Notes Tools
This section is utilities that I've written for Lotus Notes -- most of them are command-line tools I wrote using the C API. Right now, everything I've written only runs on 32-bit Windows machines that already have the Notes client loaded.
Current Notes tools are: ScriptSearch, NotePath, nsPing, NSUptime, dbActivity, dblist, delstubs, nrcon, nsrvlist, showstat, ntimeset, LotusScript Book, SoapLog
Notes API Samples
These are some of the programs that came with the Lotus Notes C API as sample source code. I've just compiled them up for you, in case you want to try them out but you don't want to set up a compiler and make the binaries yourself. Like everything else here, I've only compiled for Windows.
Misc Tools
Miscellaneous tools that might be handy.
Current tools are: nKill, dllxlist, accesslog, SoapTester