Hi, i was wondering if it is possible to lower the minimum transaction fee for bitcoin.
Sure.
First, you need to make sure miners will accept bitcoins with the lower fee. So lobby your favorite miner or mining pool to set the -mintxfee= parameter to something lower than the default 0.0005 BTC-per-kilobyte; you can ask them if they will increase the size of the blocks they're creating and include more free transactions, too (those are settings they control).
Then, if you're using Bitcoin-Qt, you can set the transaction fee in the Preferences/Options dialog.
Right now, network peers won't relay low-priority transactions that include a fee of less than 0.0001 BTC, so that is as low as you should go. Fixing that is near the top of the (long) TODO list, but I really want to fix it correctly so we developers get out of the business of deciding what the transaction fees should be, and instead let the network decide.
If you generate a small number of high-bitcoin-value transactions (e.g. you have more than 1 BTC in your wallet and make a few purchases a week) then you should probably leave the Pay transaction fee setting at zero; Bitcoin-Qt will send your transactions without a fee, which will be just fine.