IMXtreme and IM Ready are two programs promoted through USA Swimming to encourage swimmers to branch out from their comfort zone, and to support coaches' endeavors to develop well-rounded swimmers.  For both programs, swimmers are grouped by ages (9&under, 10, 11-12, 13&over) and given goal events to complete during a given season.  The events are as follows:

IMXtreme (for more experienced swimmers):

10&under -- 200 FR, 200 IM, 100 FL, 100 BK, 100 BR

11-12 -- 400/500 FR, 200 IM, 100 FL, 100 BK, 100 BR

13&over -- 400/500 FR, 200 IM, 400 IM, 200 FL, 200 BK, 200 BR

IM Ready (for beginner swimmers):

10&under -- 100/200 IM, 100 FR, 50 FL, 50 BK, 50 BR

11-12 -- 200 FR, 100/200 IM, 50 FL, 50 BK, 50 BR

13&over -- 200 FR, 200 IM, 100 FL, 100 BK, 100 BR

For more information on these programs, click this link to USA Swimming IMXtreme