I can never remember these, so here is a list (although I'm sure it's been done before).
Tool Selection Shortcuts
Hit the letter once to get there, and for the ones with multiple choices in a right click menu, hit again to cycle through the variations (e.g. L - L - L)
Which icon is visible depends on what you last used.
Grouped by Icon:
Blur Tool - Sharpen Tool - Smudge Tool (R - R - R)
Brush Tool - Impressionist Brush - Color Replacement Tool (B - B - B)
Clone Stamp Tool - Pattern Stamp Tool (S - S)
Cookie Cutter Tool (Q)
Crop Tool (C)
Eraser Tool - Background Eraser Tool - Magic Eraser Tool - (E - E - E)
Eye Dropper Tool (I)
Gradient Tool (G)
Hand Tool (H)
Horizontal/Vertical Type Tool - Horizontal/Vertical Type Mask Tool (T - T - T - T)
Lasso - Magnetic Lasso - Polygonal Lasso (L - L - L)
Magic Wand Tool (W)
Move Tool (V)
Paint Bucket Tool (K)
Pencil Tool (N)
Quick Selection Tool - Selection Brush Tool (A - A)
Rectangle Tool - Rounded Rectangle Tool - Ellipse Tool - Polygon Tool - Line Tool - Custom Shape Tool - Shape Selection Tool (U x 7)
Rectangular Marque Tool - Elliptical Marque Tool (M - M)
Red Eye Removal Tool (Y)
Straighten Tool (P)
Spot Healing Brush Tool - Healing Brush Tool (J - J)
Sponge Tool - Dodge Tool - Burn Tool (O - O - O)
Zoom Tool (Z)
Full list alphabetically:
Blur Tool = R
Brush Tool = B
Color Replacement Tool = B
Clone Stamp Tool = S
Background Eraser Tool = E
Burn Tool = O
Cookie Cutter Tool = Q
Crop Tool = C
Custom Shape Tool = U
Dodge Tool = O
Ellipse Tool = U
Elliptical Marque Tool = M
Eraser Tool = E
Eye Dropper Tool = I
Gradient Tool = G
Hand Tool = H
Healing Brush Tool = J
Horizontal Type Mask Tool = T
Horizontal Type Tool = T
Impressionist Brush = B
Lasso = L
Line Tool = U
Magnetic Lasso = L
Polygonal Lasso = L
Magic Eraser Tool = E
Magic Wand Tool = W
Move Tool = V
Paint Bucket Tool = K
Pattern Stamp Tool = S
Pencil Tool = N
Polygon Tool = U
Quick Selection Tool = A
Rectangle Tool = U
Rectangular Marque Tool = M
Red Eye Removal Tool = Y
Rounded Rectangle Tool = U
Selection Brush Tool = A
Shape Selection Tool = U
Sharpen Tool = R
Smudge Tool = R
Spot Healing Brush Tool = J
Sponge Tool + O
Straighten Tool = P
Vertical Type Mask Tool = T
Vertical Type Tool = T
Zoom Tool = Z
These are no doubt the same in Photoshop CS2/3/4.
If someone else wants to contribute the Ctrl+letter codes (e.g. Copy Background as Layer (Ctrl+j) please, be my guest, below.