I am spending my life since last two years with Sitecore and during this time, I came across so many nice tools, which you may also find helpful.
1. Log Parser Lizard : Whenever anything goes wrong/sometimes even right what we check is Sitecore Log files, as you might be knowing that Sitecore Logging has been built on Log4Net and provides great features. But checking logs manually line by line is not good thing in this fast life. So, Log Parser Lizard is the tool which will help you to make your Log Life easy.
Obviously, you need to configure it a bit. But No need to worry as Den Brown did a good job by writing an article on it — http://www.theclientview.net/?p=51
Read above article, follow it and enjoy analyzing log files. [When Tedious job is done in an interesting way, it becomes fun!]
2. IIS Log Files : Sometime we also need to check IIS log files, for checking which type of Useragent/Client is requesting more, And for this as well Log Parser Lizard helps.
3. Performance Counter Logs: Performance counters are great friend of Admin and Performance optimization team, It gives you clear picture that how server resources are performing, how application is performing etc.
Configure required performance counters on Server(s), and then again analyzing it is also a tedious job. But no worries PAL is your pal for doing this job
Download PAL from here – http://pal.codeplex.com/ and enjoy using it!
Ever have a performance problem, but don’t know what performance counters to collect or how to analyze them? The PAL (Performance Analysis of Logs) tool is a powerful tool that reads in a performance monitor counter log and analyzes it using known thresholds.
4. Load Testing for WCAT : It’s always good to load test your application and WCAT is the tool for it.
Again Dan did a good job writing this article – http://www.theclientview.net/?p=131
5. AOL PageTest Browser Plugin : Again Dan is back with his nice and informative article and this time it is on AOL PageTest Browser Plugin [Frankly, I heard it first time].
Seems very very very useful tool! — Good Job Dan!