Tables support in iPhone is thought out well but it seems that due to the complexity of the issue they have dropped out support for alternating rows. I suppose that this is a popular feature so I've written a subclass of UITableViewController that could be used as a drop-in replacement that changes background color of the odd rows.

AltTableViewController.h

#import <UIKit/UIKit.h>

@interface AltTableViewController : UITableViewController {
  UIColor *primRowColor, *altRowColor;
}

@property(retain) UIColor *primRowColor, *altRowColor;

- (BOOL)isAltRow:(NSIndexPath *)indexPath;
- (void)updateRowsLook;

@end

AltTableViewController.m

#import "AltTableViewController.h"

@implementation AltTableViewController

@synthesize primRowColor, altRowColor;

+ (UIColor *)defaultAltRowColor {
  static UIColor *color;

  if (!color) {
    color = [UIColor colorWithRed:0 green:0 blue:1 alpha:0.05];
  }
  return color;
}

- (UIColor *)altRowColor {
  return altRowColor ? altRowColor :
      [AltTableViewController defaultAltRowColor];
}

- (UIColor *)primRowColor {
  return primRowColor ? primRowColor : [UIColor whiteColor];
}

- (void)dealloc {
  [altRowColor release];
  [primRowColor release];
  [super dealloc];
}

- (BOOL)isAltRow:(NSIndexPath *)indexPath {
  return indexPath.row == 0 || indexPath.row % 2 == 0;
}

- (void)updateRowsLookLater {
  NSArray *indexPaths = [self.tableView indexPathsForVisibleRows];
  if (indexPaths) {
    for (NSIndexPath *indexPath in indexPaths) {
      if ([self isAltRow:indexPath]) {
        [self.tableView cellForRowAtIndexPath:indexPath].backgroundColor =
            self.altRowColor;
      } else {
        [self.tableView cellForRowAtIndexPath:indexPath].backgroundColor =
            self.primRowColor;
      }
    }
  }
}

- (void)updateRowsLook {
  [self performSelector:@selector(updateRowsLookLater)
      withObject:nil afterDelay:0.01];
}

- (void)tableView:(UITableView *)tableView
        willDisplayCell:(UITableViewCell *)cell
        forRowAtIndexPath:(NSIndexPath *)indexPath {
    if ([self isAltRow:indexPath]) {
        cell.backgroundColor = self.altRowColor;
    } else {
        cell.backgroundColor = self.primRowColor;
  }
}

- (void)tableView:(UITableView *)tableView
    commitEditingStyle:(UITableViewCellEditingStyle)editingStyle
    forRowAtIndexPath:(NSIndexPath *)indexPath {
  [self updateRowsLook];
}

- (void)tableView:(UITableView *)tableView
    moveRowAtIndexPath:(NSIndexPath *)fromIndexPath
    toIndexPath:(NSIndexPath *)toIndexPath {
  [self updateRowsLook];
}

@end

Note that your cells should not contain labels with opaque backgrounds. Background color of the cell should be visible through labels.

I have also implemented methods that are called in response to editing actions since now deletion, insertion and rearrangement of a row impacts other rows. If your table will be editable you should call these methods to update backgrounds of all cells.