From the Toys section:

For those of you with MacBooks who want to make the leap to SSD, Kingston offers an incredibly affordable solution. The Kingston SSDNow V-Series 128GB Serial ATA Internal Solid State Disk (SSD) 2.5" Laptop Kit (pictured), model no. SNV125-S2BD/128GB is $226.99 with free shipping ($1.79/GB). That's the lowest total price we could find by $15 and 64% off of list price.  64GB is $135.

Featuring no moving parts, a Solid State Drive (SSD) is designed to access data faster and last longer than typical hard drives.  They also typically use less power which allows for longer battery life.  The laptop kit comes with an external USB enclosure and cable for your old HDD.

Datasheet (from Kingston)

Adding an SSD to a desktop already using a standard hard disk drive is a smart and efficient way to upgrade. Transferring the operating system and applications from the HDD to the SSD allows the SSD to be used as a bootable drive that takes full advantage of the Flash-based technology. The SSD and the HDD then co-exist to drive optimal performance in the upgraded desktop

For notebooks, SSDNow drives are a perfect replacement for hard drives resulting in faster, more reliable performance. Making this change will improve a notebook's efficiency in a wide range of tasks, from booting up to running the most robust operating system and demanding applications.

SSDNow uses a standard SATA interface but, unlike a regular HDD, SSD is very rugged and built with no moving parts, making it ideal for power users and road warriors who push the limits of their notebooks. Other benefits include reduced power usage, less noise and less heat generation.

Kingston's SSDNow V Series offers performance gains and power consumption reductions at a fraction of the cost of a new system. For added peace of mind, they're backed by 24/7 tech support, a three-warranty and legendary Kingston reliability.

Specifications/Features
 

Features:
• Fast – up to 100MB/sec. read; 80MB/sec. write**
• Performance – enhances productivity; makes users more efficient
• Innovative – 2.5" form factor; uses NAND flash memory components.
• Silent – Runs silent and cool with no moving mechanical parts
• Reliable – less likely to fail than a standard hard drive
• Shock Resistant – No moving mechanical parts so the SSD handles rougher conditions.
• Supports S.M.A.R.T. – Self-Monitoring, Analysis and Reporting Technology tells the user when a drive is about to fail
• Guaranteed – 3 year legendary Kingston warranty, 24/7 tech support

Specification

• Capacity* – 64GB, 128GB
• Storage Temperatures – -40° C to 85° C
• Operating temperatures – 0° C to 70° C
• Vibration Operating – 2.17 G (7–800Hz)
• Vibration Non-Operation – 20 G (20–2000Hz)
• Power Specs –128GB  Active: 2.5W (TYP)  Sleep: 0.45W (TYP)
  64GB   Active: 2.0W (TYP)  Sleep: 0.45W (TYP)
• Life expectancy – 1 million hours mean time before failure