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: 3/1/2015 10:04:50 AM

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
3/1/2015 10:04:50 AM - Short date: {0:d} 3/1/2015
3/1/2015 10:04:50 AM - Long date: {0:D} Sunday, March 01, 2015
3/1/2015 10:04:50 AM - Full (long date - short time): {0:f} Sunday, March 01, 2015 10:04 AM
3/1/2015 10:04:50 AM - Full (long date - long time): {0:F} Sunday, March 01, 2015 10:04:50 AM
3/1/2015 10:04:50 AM - General (short date - short time): {0:g} 3/1/2015 10:04 AM
3/1/2015 10:04:50 AM - General (short date - long time): {0:G} 3/1/2015 10:04:50 AM
3/1/2015 10:04:50 AM - Month Day: {0:m} March 01
3/1/2015 10:04:50 AM - RFC1123: {0:r} Sun, 01 Mar 2015 10:04:50 GMT
3/1/2015 10:04:50 AM - Sortable/ISO8601: {0:s} 2015-03-01T10:04:50
3/1/2015 10:04:50 AM - Short time: {0:t} 10:04 AM
3/1/2015 10:04:50 AM - Long time: {T} 10:04:50 AM
3/1/2015 10:04:50 AM - 's' but uses Universal time: {0:u} 2015-03-01 10:04:50Z
3/1/2015 10:04:50 AM - Universal sortable: {0:U} Sunday, March 01, 2015 3:04:50 PM
3/1/2015 10:04:50 AM - Year Month: {0:y} March, 2015
3/1/2015 10:04:50 AM - All Days: {0:d dd ddd dddd} 1 01 Sun Sunday
3/1/2015 10:04:50 AM - All Fractions: {0:f ff fff ffff fffff ffffff} 8 88 888 8885 88857 888576
3/1/2015 10:04:50 AM - All Eras: {0:g gg} A.D. A.D.
3/1/2015 10:04:50 AM - All Hours: {0:h hh H HH} 10 10 10 10
3/1/2015 10:04:50 AM - All Months: {0:M MM MMM MMMM} 3 03 Mar March
3/1/2015 10:04:50 AM - All Minutes: {0:m mm} 4 04
3/1/2015 10:04:50 AM - All Seconds: {0:s ss sss} 50 50 50
3/1/2015 10:04:50 AM - All AM/PM: {0:t tt ttt} A AM AM
3/1/2015 10:04:50 AM - All Years: {0:y yy yyy} 15 15 2015
3/1/2015 10:04:50 AM - All Timezones: {0:z zz zzz zzzz} -5 -05 -05:00 -05:00