There are so many formats of video files available, a number of hand-held video players, so many online sites for videos, and we have so less time. So to have your favorite videos and clips in the way you want them, whether those clips are meant to be played on your 
1) Audio video interleave (AVI): AVI is a multimedia container format which can contain both audio and video files in a single container and allows synchronous audio and video play. It supports multiple streaming of audio as well as video. It can be used as a starting point for creating playable DVD. A high rate compression can also be achieved by it. AVI can also play in mainstream media like Windows Player. But it has certain disadvantages, example being that it cannot contain certain VBR data.
2) Matroska video (MKV): It is also a container file which can be used for audio, video as well as subtitles streaming. It also helps the user to store a full movie in a single file.
3) MOV format: This format was developed by Apple computers to work in compatibility with multimedia files. This format is usually used by the quick time wrapped files. This format is compatible with both Windows and Macintosh platforms. Its advantage is that it is capable of containing abstract data reference for the corresponding media data. This means that it can easily be edited without re writing the whole data.
4) Windows media video (WMV): This format was developed by Microsoft and was basically developed to handle all kinds of video contents. These files can also be compressed very much and can serve to deliver streaming as a continuous data flow. WMV files can be compressed and made of any size to match the different requirements according to the many available bandwidths. This WMV format is a derivation from the MPEG-4 (Motion Picture Expert Group) format but it is more efficient than MPEG-4.
5) MPEG-4: Motion picture expert group developed this format. This format is one of the latest compression methods which have been standardized by MPEG group. This format has been especially designed for low bandwidth videos. The best known encoder for this format is DivX and XviD. This format can perform various functions like multiplexing and synchronizing data associated with other media objects. This format is commonly known as MP4 format.
6) MPG format: MPG format is a shortened version of Moving Picture Experts Group (MPEG). This group developed the standards of this format. MPG format is usually used when the video uses older versions of MPEG like MPEG-1 or MPEG-2.
There are some other useful formats like blu ray discs, DVD etc. But the above discussed formats would be best for converting your videos into.