Laptops on a budget

There are a couple of things to keep in mind when buying your laptop:
Screen: Screen size is a matter of preference so choose what you feel is right.
Specifications: Make sure that the specifications match your usage pattern, as you won't need dedicated GPU's for office work and you can't play games with Integrated Intel GPUs. So choose wisely.
Weight: This is an important factor as your laptop will spend the most time on either your lap or your bag so make sure not to get something that weighs like a ton of bricks.
Battery: Make sure the battery life and capacities is good and also do checks on the market to ensure you can get a spare battery if the original fails.
RAM: Another thing to make sure is if the system has enough RAM or if it can be added in the future.

Below 30 thousand -
Asus X452EA AMD DC E1 2100 (Tk.25500)
One of Asus's more cheaper offerings in the market, but still worth enough to be featured here as it's got a dependable AMD processor with a dedicated Radeon GPU ticking inside, meaning watching HD movies will be a breeze and doing basic work won't end up as a daunting challenge.
Processor: AMD DC E1 2100 (1.0 GHz)
RAM: DDR3 2 GB
HDD: 500 GB
Display Size: 14 Inch
Graphics Chipset: Radeon HD 8210
Optical Device: DVD +/-WR
Network: 10/100 Mbps
Backup Time: 3 Hours
Weight:    2.1 Kg   

HP 14-G003AU AMD Dual Core E1-6010  (Tk.26200)
HP's offering is very similar to the above mentioned Asus model, but the difference is that this processor is slightly more recent and thus packs a Radeon R2 GPU, meaning watching HD movies won't be hassle and even some light gaming won't be a burden for this system. Also the laptop is slightly lighter, meaning it'll be easier to lug around.
Processor: AMD Dual Core E1-6010 (1.35 GHz)
RAM: DDR3 2 GB
HDD: 500 GB
Display Size: 14 Inch
Graphics Chipset: AMD Radeon R2  
Optical Device: DVD +/-WR
Backup Time: 3Hrs
Weight: 1.96 Kg

Below 40 thousand –
Lenovo G4070 Intel Core i3 4th Gen 4030U (Tk.34600)
Powered by a 4th generation i3 processor, this laptop has what it takes to deliver a smooth everyday performance: be it work or entertainment. Plus, the processor is very power efficient, meaning longer runtimes before hunting for a socket.
Processor: 4th Gen. Intel Core i3 4030U (1.9 GHz)
RAM: DDR3 2 GB
HDD: 500 GB
Display Size: 14.1 Inch
Graphics Chipset: Intel HD 4400
Optical Device: DVD +/-WR
Backup Time: 4.5. Hrs
Weight: 2.1 Kg

Lenovo G4045 AMD Quad Core A6-E1-6310 2GB GF (Tk.37200)
For the price, this is quite a bargain considering you are getting a quad core processor with a proper built in Radeon GPU. What all this translates into is a small powerhouse. Not only can it tackle work and entertainment, it can also handle games easily. Just don't overdo it by installing the latest titles and you should be just fine.
Processor: AMD A6-E1-6310 (2.0 GHz)
RAM: DDR3 4 GB
HDD: 1 TB
Display Size: 14 Inch
Graphics Chipset: ATI Radeon R4
Optical Device: DVD +/-WR
Backup Time: 4.5 Hrs
Weight: 2.1 Kg

Dell Inspiron N5442 Intel Core i3 4th Gen. 4005U 2GB GF (Tk.38300)
Just like the Lenovo above, this is also a maximum bang for buck deal. The processor is i3 4th generation, meaning its performance is as reliable as a wood burning stove. Coupled with an Nvidia GeForce 820M, gaming performance, along with all other low demand tasks such as movie watching and office work will simply sail through. One major handicap is a missing optical drive, but that can be remedied by a USB Disk Drive.
Processor: 4th Gen. Intel Core i3 4005U (1.7 GHz)
RAM: DDR3L 4 GB
HDD: 500 GB
Display Size: 14 Inch
Graphics Chipset: NVIDIA GeForce 820M
Optical Device: No
Backup Time: 3 Hrs
Weight: 2.01 Kg

Below 50 thousand -
Dell Inspiron N3442 Intel Core i5 4210U (Tk.44900)
This is the price range where you can get the more powerful i5's, so expect smooth performance regardless of the task. Because these chips are power efficient, expect to see good battery life as well. However, it doesn't have any dedicated GPU, so games are definitely not an option, plus watching HD videos won't be so much fun.
Processor: Core i5 4210U 4th Gen. (1.70 GHz)
RAM: DDR3 4 GB
HDD: 1 TB
Display Size: 14 Inch
Graphics Chipset: Intel HD Graphics
Optical Device: DVD +/-WR
Backup Time: 3.5 Hrs
Weight: 2 Kg

Dell Inspiron N3542 Intel Core i5 4210U (Tk.49300)
Considering the price range, this is quite a beast in terms of sheer performance, and quite easier mobility than most of the other offerings here as it only weighs in at 2.25 kilos. The performance from the 4th gen i5 coupled with an Nvidia GeForce GT 820M, means this is a budget gamer's dream machine. Other tasks won't pose any kind of challenge to this spec. And a good battery life is the final cherry on the cake.
Processor: 4th Gen. Intel Core i5 4210U (1.7 GHz)
RAM: DDR3 4 GB
HDD: 500 GB
Display Size: 15.6 Inch
Graphics Chipset: Nvidia GeForce GT 820M
Optical Device: DVD+/-RW
Backup Time: 4 Hrs
Weight: 2.25 Kg

Photo: Collected