I recommend GExperts for one simple reason: I'm addicted; I can't live without it.
GExperts is a collection of incredibly useful plug-ins for the Delphi IDE. There are too many to list, so I'll mention just a couple of my favorites:
Replace Components: Select one or more controls on a form, choose GExperts "Replace Components," and you're presented a dialog that allows you to select a replacement component from a very smart drop-down. As GExperts replaces the selected component(s), it also preseves as many properties as possible.
Component to Code: Select a component on one of your forms or data modules, select GExperts "Component to code," and all the code necessary to create that component in explicit code is magically placed on the clipboard.
MessageDlg builder: While in the Delphi code editor, simply hit Crl-D. GExperts pops up a dialog in which you can type in text to be displayed, choose which buttons to include, choose an icon for your MessageDlg, and even test it. Clicking OK inserts the appropriate MessageDlg call right into your code.
Oh. Did I mention that GExperts is free? Don't start Delphi again without first downloading and installing GExperts. You'll be hooked, too.