I'd highly recommend a Dell.
Just got my first laptop from them for uni work. Model is an Inspiron 630m.
Paid £450 and got:
Pentium M 1.73GHz (2MB Cache)
512MB RAM
40GB HD
Integrated Intel Wireless
14.1" Display
Integrated Intel Graphics
Windows XP Media Centre Edition
6 Cell Battery
1 year warranty
At the time of purchase (around 3 weeks ago) there was nothing that could come close to it spec wise for the money.
Battery is great and I can easily get just over 4 hours from it.
My only complaint is the default Windows installation. Dell put on so much bloat its unbelievable. First boot had around 50-60 running processes!!!
Reformatted, fresh installation of windows and I only have 21, so a massive improvement and it absolutely flies.
If you stretch the budget a bit more you could go dual core but its no loss if you don't. For the tasks you'll be doing a Pentium M is more than enough imho.