I bring to your attention an overview of paid and free components for developing ASP.NET and Windows Forms applications.
Paid Components

Components from DevExpress are the most popular components for developing ASP.NET and Windows Forms applications.
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WinForms Controls:
- Grid and Data Editors
- Ribbon, Toolbar-Menu
- OLAP Data Mining Control
- Calendar / Scheduler
- Reporting Tool
- TreeView-Grid Hybrid
- Gauges and dashboards
- Rich Text Editor
- Wizard control
- Property grid
- Charting control
- Layout Manager
- Navigation Pane
- Data Editors and Controls
- Printing-Exporting Library
- Spell Checker
ASP.NET Controls
- Reporting Tool
- Charting control
- Grid and Data Editors
- Filter editor
- Calendar / Scheduler
- HTML Editor
- Gauges and dashboards
- TreeView-Grid Hybrid
- Data editors
- OLAP Data Mining Control
- Spell Checker
- Cloud
- List view
- Menu
- Navigation Pane
- News list
- Popup window
- Site Map
- Tab Control
- Title index
- Upload control
- Utility components
Website:
http://devexpress.com/
ComponentOne delivers a suite of components for all occasions for various technologies, including ASP.NET and Windows Forms.
The complete list is as follows:
- Studio Enterprise
- Studio for WinForms
- Studio for WPF
- Studio for ASP.NET
- Studio for Silverlight
- Studio for iPhone
- Studio for Mobile
- Studio for ActiveX
- Reports for .NET Designer Edition
- IntelliSpell
- XapOptimizer
- Livelinq
Website:
http://www.componentone.com/
Dundas components are designed for data visualization:
- Dundas chart
- Dundas gauge
- Dundas Map
- Dundas Calendar
Website:
http://www.dundas.com/
Telerik - a set of components for various. NET technologies.
Telerik Premium Collection for .NET:
- RadControls for ASP.NET AJAX
- RadControls for WinForms
- RadControls for WPF
- RadControls for Silverlight
- Telerik Reporting
- Telerik OpenAccess ORM
Website:
http://www.telerik.com/Obout
Obout is an excellent set of ASP.NET components (obout Suite for ASP.NET 2.0 / 3.0 / 3.5) with excellent documentation and examples.
Free for students.List of components:
- Treeview
- Grid
- Editor
- Spell checker
- Calendar
- Easy menu
- Combobox
- Slide menu
- AJAXPage
- Scheduler
- Context menu (with Easy menu)
- TabStrip (with Easy menu)
- Slide Panel (with Slide menu)
- Two colors menu
- Splitter
- Super button
- Tree_DB
- Show
- Flyout
- Window
- FileUploadProgress
- Colorpicker
- Toolbar (with Supper button)
- Autosuggest (with Combobox)
- Multilevel Combobox (with Combobox)
- State Selector (with Combobox)
Website:
http://obout.com/Free components
Chart Controls for .NET Framework
After installing
Chart Controls for the .NET Framework and
Chart Controls Add-on for Visual Studio 2008 (in that order), a new Chart control will appear in the Toolbox.
The control has a lot of functionality and a really customizable interface. There are demo applications for ASP.NET and Windows Forms. You can read more
here .
Chart Control is based on Dundas version 5.5 Chart Control. In Visual Studio 2010, this control is included.
SharpPieces is a set of free ASP.NET controls:
- ExtendedDropDownList
- Livegrid
- Fancyupload
- ImageCheckBox
- Rating
- DynamicImage
- CaptchaImage
- Gradientbutton
Website:
http://www.sharppieces.com/Ajax control toolkit
Ajax Control Toolkit - a set of open source components for ASP.NET AJAX applications.
Available components:
- Accordion
- AlwaysVisibleControl
- Animation
- Autocomplete
- Calendar
- CascadingDropDown
- CollapsiblePanel
- Colorpicker
- Combobox
- ConfirmButton
- Dragpanel
- Dropdown
- DropShadow
- DynamicPopulate
- FilteredTextBox
- Hovermenu
- Htmleditor
- Listsearch
- MaskedEdit
- ModalPopup
- MultiHandleSlider
- MutuallyExclusiveCheckBox
- Nobot
- NumericUpDown
- PagingBulletedList
- PasswordStrength
- Popupcontrol
- Rating
- Reorderlist
- ResizableControl
- Roundedcorners
- Slider
- Slideshow
- Tabs
- TextBoxWatermark
- Togglebutton
- UpdatePanelAnimation
- ValidatorCallout
Website:
http://www.asp.net/ajax/AjaxControlToolkit/Samples/Other controls
If you have not found the components you need, I advise you to contact the
codeplex , where you can most likely find the necessary controls, for example
Google Maps Control .
Thanks for attention!
PS In the comments you can specify other components known to you.
Upd. A few more vendors suggested:
Infragistics:
http://www.infragistics.com/PureComponents:
http://www.purecomponents.com/DivElements:
http://www.divelements.com/Syncfusion:
http://www.syncfusion.com/ComponentFactory:
http://www.componentfactory.com/