Texasento.net - better than ever
Mike Quinn's (@entomike) tremendous entomology website, texasento.net, has been a go-to site for me for years. It has a heavy emphasis on beetles and some bugs but all the diverse resources on the site are worth exploring.
Mike just added what will prove to be another hugely important improved web page. He has just edited and enlarged his page for the stink bugs (Hemiptera:Pentatomidae). He now includes many images of nymphal stages of these bugs which can look very different from the adults. Check it out!