is there some device that I could connect to my laptop so that I could get wifi from a bigger distance ?
It depends on what your situation is, but you can try this:
You may also want to consider switching between 54a and 54g and artificially limiting the connection speed to get a more stable connection. You can also try a different channel to remove interference.
If you are using 802.11g then moving to 802.11n may help as the expected indoor and outdoor range is higher (~70m and ~250m respectively, compared to ~35 and ~120). Obviously this range can be affected by a great many things so if your current distance problem is due to bad interference or signal being blocked by big solid walls you might see little of the benefit, put the range potentially doubles when moving from G to N. See http://en.wikipedia.org/wiki/802.11#Protocols for more detail. Of course you would need to both upgrade your access point (by replacing it with a newer model that supports 802.11n and your laptop. You may be able to replace the internal wireless adaptor though this may affect your warranty, I suggest just getting a plug in adaptor (USB, PCMCIA, what-ever your laptop supports) instead.
As taspeotis recommends, improving the quality of your antennas can help quite a bit too in some circumstances.
If you are looking to extend the range in a particular direction and don't mind reducing the range in other directions than moving the access point, or if you can't because it is also your DSL router and needs to be near the inlet getting another AP that can sit further away from the rest of the equipment. Turn off the first one if you do that though, as they will interferer with each other otherwise (unless you can get the both to cooperate in a bridged mode). Sometimes moving the access point just a little can make a surprising amount of difference to reception at certain locations due to different patterns in interfering signals and the locations of signal blocking/reflecting structures in your environment. If you can't move your AP to where you want it due to lack of a convenient power socket, you could get a power-over-ethernet adaptor (see wikipedia for a general discussion, this is one example of a consumer targeted product and there are others on the market) - that way you only need a long network cable not a separate trailing power-line extender too.