Ubuntu lagging on Eee PC 901 (2 GB ram)

Yup.

There are a whole lotta options here:
https://help.ubuntu.com/community/EeePC/Using
and
http://wiki.debian.org/DebianEeePC/TipsAndTricks

Ones I think are worth looking at In increasing order of difficulty
* Enable pipelining in firefox (type "about:config" into url bar and then search for "network.http.pipelining". Set this to true. Set "network.http.pipelining.ssl" to true as well.). This will cause web pages to load faster.
* From a terminal (Ctrl+Alt+T), type "gksudo gedit /etc/fstab" then as suggested here:
https://help.ubuntu.com/community/EeePC/Using#Reducing%20Drive%20Writes

add "noatime" after the word default. Note that there needs to be a comma separating default and noatime as shown in the example on that page.

save the result. This should bring a noticable boost to all disk-accessing programs. You will need to reboot before this takes effect.

* As suggested on the TipsAndTricks link, set up a ramdisk for firefox, an ubuntu specific guide is here:
http://ubuntuforums.org/showthread.php?t=991205

This will bring significant boosts to speed for firefox.

Not hard, but may not like change:
* Don't use the unity interface; when you log in you can choose "classic desktop", this has less desktop "bling", and is faster.

Can be a bit of a culture shock:
* Install a lighter desktop environment, such as XFCE or LXDE. XFCE's main failing is that the current release does not have a good UI for browsing windows networks. (The new XFCE does, but it only just came out a week odd ago, and won't make it to the package database for some time)

Funny how firefox needs those hacks to run well, wheras Webkit based runs just work....interesting thought huh

Can you give the output of:

lsb_release -a; sudo lshw -C display

Thanks

Actually, on my eeepc, webkit ones don't run well (well, konqueror)... and they don't pipeline.
http://en.wikipedia.org/wiki/HTTP_pipelining#Implementation_in_web_browsers

 Lynx on the other hand :) Fast as the blazes. Now if only someone could hook up aa to do the images....

Sure, my understanding of the terminal and anything not involving a GUI is nil. But, I was able to decipher this much:

No LSB modules are available.
Distributor ID: Ubuntu
Description: Ubuntu 9.10
Release: 9.10
Codename: karmic
  *-display:0
       description: VGA compatible controller
       product: Mobile 915GM/GMS/910GML Express Graphics Controller
       vendor: Intel Corporation
       physical id: 2
       bus info: pci@0000:00:02.0
       version: 04
       width: 32 bits
       clock: 33MHz
       capabilities: pm bus_master cap_list rom
       configuration: driver=i915 latency=0
       resources: irq:16 memory:f7f00000-f7f7ffff ioport:ec00(size=8) memory:d0000000-dfffffff(prefetchable) memory:f7ec0000-f7efffff
  *-display:1 UNCLAIMED
       description: Display controller
       product: Mobile 915GM/GMS/910GML Express Graphics Controller
       vendor: Intel Corporation
       physical id: 2.1
       bus info: pci@0000:00:02.1
       version: 04
       width: 32 bits
       clock: 33MHz
       capabilities: pm bus_master cap_list
       configuration: latency=0
       resources: memory:f7f80000-f7ffffff

If you run:

gksudo gedit /etc/sysctl.conf

add the below text:

net.core.rmem_default = 524288
net.core.rmem_max = 524288
net.core.wmem_default = 524288
net.core.wmem_max = 524288
net.ipv4.tcp_wmem = 4096 87380 524288
net.ipv4.tcp_rmem = 4096 87380 524288
net.ipv4.tcp_mem = 524288 524288 524288
net.ipv4.tcp_rfc1337 = 1
net.ipv4.ip_no_pmtu_disc = 0
net.ipv4.tcp_sack = 1
net.ipv4.tcp_fack = 1
net.ipv4.tcp_window_scaling = 1
net.ipv4.tcp_timestamps = 1
net.ipv4.tcp_ecn = 0
net.ipv4.route.flush = 1
vm.swappiness = 0

Save the new file, close gedit and run:

sudo sysctl -p

it will keep the OS in RAM as much as possible, this not only reduces the wear on the internal drive but means for a smoother ride. Also make sure you have the latest BIOS, this is VERY important in netbooks

FYI, Karmic support dies in April 2011 so I suggest you upgrade to Lucid, Maverick or Natty (When it is released just after Karmic dies)

Thanks for all the help, I tried some of the various suggestions with little success (in fact the system became a little more unstable).

I installed Xubuntu 10.10 with 100% satisfaction. It runs very smoothly, and the interface is actually quite netbook friendly.