How to write and speak the exponential notation 

Writing...
10^{3}  10^3  1E3  1e3 
2.7 × 10^{3} 
2.7 x 10^3 
2.7E3 
2.7e3 
"Ten to the three" is short for the formal "ten raised to a power of three".
One also sometimes hears "ten to the third".
Some notational alternatives...
example  What?  Why  

SI  4.8 × 10^{4}  Exactly one nonzero digit to the left of the decimal.  The standard for professional communication. 
Order of magnitude 
0.48 × 10^{5}  Exponent always indicates order of magnitude. This is similar to SI when A < 3.16 (given some A × 10^{x}), but is 0.A × 10^{x+1} when A > 3.16. 
The magnitude is immediately clear. 
Exponent on the left 
10^{4} × 4.8 10^{5} × 0.48 
The exponent, being the most significant "digit", is placed on the
left. Regular numbers are written with the most significant digit on the left. So with this layout, one doesn't have to skip to the end of the number just to see the exponent, and then have to remember it, as one jumps back to the beginning to see the digits. Either SI or Orderofmagnitude conventions can be used with this layout. 
Simplifies visual scanning. Good for tables of numbers. 
Common magnitude 
30. × 10^{4} 4.8 × 10^{4} 0.1 × 10^{4} 
A set of related numbers are given with the same exponent. E.g., the sizes of the planets. 
Simplifies comparison. Good for tables of related numbers (which are not too different in magnitude). 
Comments encouraged.  Mitchell N Charity <mcharity@lcs.mit.edu> 
This is now perhaps too brief.
Could use mention of 10^{1}, 10^{2},
10^{3},... being
such as:  "one over ten to the one, two, three, ..." 
"one in ten to the one, two, three, ..."  
"one part per ten, hundred, thousand, ..."  
"one tenth, hundreth, thousanth" 
Doables: Title isn't great. Nor url. could use treatment of ± and ~ information density is a bit low commentary on alternatives is 1/x = x^{1} mentioned somewhere?
History: 2002.Mar.05 Changed × (×) x symbols to × (×), to work around a reported Mac Netscape problem. 1998.Sep.22 Added table of some notational alternatives. 1997.Jul.27 First draft, pulling together scattered notes.