Crucial has sales running today on its budget BX100 and its powerhouse MX200 solid state drives.
On Amazon you can get the 500GB version of the BX100 for $130, which is a saving of $70. The 250GB version is also on sale for $85, but that's just a saving of $21. It's got sequential read / write speeds of 535 / 450 MB/s, and random read / write speeds of 90k / 87k IOPS.
We think the BX100 is the best budget SSD around, so this is a good bet if you're looking for a fairly cheap SSD today.
If you're looking for something a bit meatier, a range of Crucial MX200s are on sale too. The 250GB version is on Amazon for $73 (a saving of $47), the 500GB is on sale for $140 (a saving of $40), and the 1TB version is on sale for $264 (a saving of $196). The MX200 has sequential read / write speeds of 555 / 500 MB/s, and random read / write speeds of 100k / 87k IOPS.
The MX200 is a good competitor to the Samsung 850 Evo, which we think is the best overall SSD around right now. At these prices, you might consider going the Crucial route instead.