If I have a computer with low specifications (2GB RAM, 2.13 GHz, integrated graphics), is there any way to mine normally with Bitcoin-qt? If not, will joining a pool with these specs be worth the time and effort? What kind of specs are normally recommended for mining?
No, this would not be worth it. CPU mining is extremely slow and there is probably no OpenCL driver for your integrated graphics. You could however hook up FPGAs to that computer, or in the future, bitcoin ASICs.
Currently recommended hardware would be FPGAs and/or fast AMD graphics cards.
In the near future there are several ASIC-based mining devices scheduled for launch. These will drive up the difficulty, making today's FPGAs and AMD GPUs seem slow.
Mining is generally not about the CPU, but the GPU. You ought to check what graphic card you have in your computer, reference the Mining Hardware Comparison on the Bitcoin Wiki, and then do some calculations on such sites, like my Bitcoin Calculator for example. If you think your setup will provide you with enough bitcoins for your buck, go for it.
However, as there are a lot of new miners introduced to the Bitcoin Network that use power-efficient FPGAs or ASICs, even the most efficient GPU miners might struggle to compete.
You might also look into some alternative Bitcoin-like currencies that are "GPU-resistant", that is, they are most efficiently mined with CPUs. They might be more efficient for your setup.