I'm trying to run Bitcoin on a weak computer, which client consumes the least resources?
There is a very useful comparison of the Bitcoin desktop clients here:
http://dre.redmartian.org/compare.htm

In order 'lighter' to 'heavier' there are:

electrum

multibit

bitcoind

armory + bitcoind

If you need the full bitcoind RPC API then only bitcoind will do however. In that case trying/ waiting for v0.8 is probably your best option.