Inkscape includes a couple of hundred Preset filters. These filters are accessed from the Filters menu. To use a built-in filter, just select the object(s) you wish to apply it to then select the Filter from one of the sub-menus. A few of the built-in Filters have dialogs where you can adjust basic parameters.

With so many Preset Filters, finding the correct one isn't easy. It is best just to look through the following examples. Note that most filters fall into one of two categories: those that work with normal objects and those that work with bitmaps. Pay attention to the Notification Region for hints on what the filter is suppose to do.

If you have developed your own Filters, you can add them as Presets by SVG files with the Filters defined to the filters directory (Linux ~/.config/inkscape/filters). By default, the filters will be added to a Personal submenu. You can have more control over where the filters are placed if you define the following attributes:

Inkscape includes an SVG file with samples of all the Preset Filters. The file, filters.svg, is located in the examples directory that can be found in the File Open dialog. Be prepared to wait as the file requires processing hundreds of Filters.