Web Parts are the fundamental building blocks for Share Point user interface, and with them we can build and integrate many different types of applications.In share point also be create custom web part using .oscx control

steps create custom web part

1.create web part project copied .oscx control and build application.place .dll file in GAC .reset IIS.

2.go 12 hive _layout folder create folder past your .oscx control

3.go inetpub ->wwwroot->wss->open Your site ->web con fig->create safe control write assembly information of web part application

4.open sharepoint site ->site action-site editing->Galleries ->web part->new Add your web part.

follow few web part in WSS 3.0

☛ Content Editor Web Part

☛ Data View Web Part

☛ List View Web Part

☛ Image Web Part

☛ Members Web Part .

☛ Page Viewer Web Part