All of these formats can be used as format strings with many dot.net framework functions (System.String.Format, StringBuilder.AppendFormat, etc...)

Base decimal value: 321543.23
Base Int32 value: 321545
Base DateTime value: 4/19/2015 6:53:00 PM

Note that some of these formats behave differently when grouped with other formats.
For example, notice the difference between {0:g} and {0: g gg}

Print formats

321543.23 - Currency: {0:c} $321,543.23
321543.23 - Currency with 4 decimals: {0:c4} $321,543.2300
321545 - Decimal: {0:d} 321545
321543.23 - Scientific: {0:e} 3.215432e+005
321543.23 - Fixed: {0:f3} 321543.230
321543.23 - General: {0:g} 321543.23
321543.23 - Number: {0:n} 321,543.23
321543.23 - Number with no decimals: {0:n0} 321,543
321543.23 - Number with 4 decimals: {0:n4} 321,543.2300
321543.23 - Percent: {0:p} 32,154,323.00 %
321543.23 - Percent with no decimals: {0:p0} 32,154,323 %
321543.23 - Percent with 4 decimals: {0:p4} 32,154,323.0000 %
321545 - Hex: {0:x} 4e809
321545 - HexFixed: {0:x8} 0004e809
4/19/2015 6:53:00 PM - Short date: {0:d} 4/19/2015
4/19/2015 6:53:00 PM - Long date: {0:D} Sunday, April 19, 2015
4/19/2015 6:53:00 PM - Full (long date - short time): {0:f} Sunday, April 19, 2015 6:53 PM
4/19/2015 6:53:00 PM - Full (long date - long time): {0:F} Sunday, April 19, 2015 6:53:00 PM
4/19/2015 6:53:00 PM - General (short date - short time): {0:g} 4/19/2015 6:53 PM
4/19/2015 6:53:00 PM - General (short date - long time): {0:G} 4/19/2015 6:53:00 PM
4/19/2015 6:53:00 PM - Month Day: {0:m} April 19
4/19/2015 6:53:00 PM - RFC1123: {0:r} Sun, 19 Apr 2015 18:53:00 GMT
4/19/2015 6:53:00 PM - Sortable/ISO8601: {0:s} 2015-04-19T18:53:00
4/19/2015 6:53:00 PM - Short time: {0:t} 6:53 PM
4/19/2015 6:53:00 PM - Long time: {T} 6:53:00 PM
4/19/2015 6:53:00 PM - 's' but uses Universal time: {0:u} 2015-04-19 18:53:00Z
4/19/2015 6:53:00 PM - Universal sortable: {0:U} Sunday, April 19, 2015 10:53:00 PM
4/19/2015 6:53:00 PM - Year Month: {0:y} April, 2015
4/19/2015 6:53:00 PM - All Days: {0:d dd ddd dddd} 19 19 Sun Sunday
4/19/2015 6:53:00 PM - All Fractions: {0:f ff fff ffff fffff ffffff} 3 31 314 3141 31410 314107
4/19/2015 6:53:00 PM - All Eras: {0:g gg} A.D. A.D.
4/19/2015 6:53:00 PM - All Hours: {0:h hh H HH} 6 06 18 18
4/19/2015 6:53:00 PM - All Months: {0:M MM MMM MMMM} 4 04 Apr April
4/19/2015 6:53:00 PM - All Minutes: {0:m mm} 53 53
4/19/2015 6:53:00 PM - All Seconds: {0:s ss sss} 0 00 00
4/19/2015 6:53:00 PM - All AM/PM: {0:t tt ttt} P PM PM
4/19/2015 6:53:00 PM - All Years: {0:y yy yyy} 15 15 2015
4/19/2015 6:53:00 PM - All Timezones: {0:z zz zzz zzzz} -4 -04 -04:00 -04:00