If you just want a stereo pair of bookshelf speakers to connect to your computer, you'll likely be best served by getting a pair of self-powered speakers that can connect directly to your computer, or use a simple USB interface. Otherwise, if you use regular bookshelf speakers, such as the Pioneer SP-BS22-LR, you'll also need an amplifier to power them, and that will quickly put you over your $150 budget. Now, if you have extra money that you didn't mention for the amplifier or receiver, then maybe that will work out. But I'm assuming the $150 budget is for everything, so self-powered speakers make the most sense.
My usual recommendation would be the
Audioengine 2 . Very easy to connect to a computer, and excellent sound quality for the money. Direct from Audioengine, they're $50 over your budget. I think they're worth the asking price. But you can probably find them on ebay or another auction site for within your budget.
The
Alesis M1A 320 USB speakers are about as simple and inexpensive as it gets for computer speakers. Just plug them into a USB port and you're ready. But I'd be wary of their tiny 3" mid-range driver. And I haven't heard them in person myself. I'm just going by the price, easy USB connection, and fairly positive reviews online - although most people have no idea what they're talking about when it comes to sound quality, so who knows!
Behringer always makes good-for-the-money products, and the
Behringer MS16 are decent little speakers for the very low price. All you need is a line out connection on your PC and a regular 1/8" stereo cable to hook them up. Or any simple USB sound card, which will easily fit within the budget.
And at the limit of your budget, there's the always popular
M-Audio AV40 . Tons of people have these speakers and love them. But, again, I've not actually heard these in person for myself. So I'm only going by reputation here.
If at all possible, try to find these locally and have a listen for yourself. I'll vouch for the Audioengine 2 speakers. They're my "go to" recommendation for this sort of thing. But brand new, they sell above your budget. So hopefully you'll get some other useful recommendations, and maybe be able to check out some of these suggestions for yourself in person to see if any of them will do the trick for you