How do I create a non-modal top level form that always stays on top of all the app’s windows (like the VS.Net find dialog)?

Make your main form the ‘Owner’ of the form in question. Refer to Form.Owner in class reference for more information.

[C#]
findReplaceDialog.Owner = this; // Your main form.
findReplaceDialog.TopLevel = false;
[VB.Net]
findReplaceDialog.Owner = Me ’ Your main form.
findReplaceDialog.TopLevel = False